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mod_perl 2.0 Server Configuration


This chapter provides an in-depth mod_perl 2.0 configuration details.

mod_perl configuration directives

Similar to mod_perl 1.0, in order to use mod_perl 2.0 a few configuration settings should be added to httpd.conf. They are quite similar to 1.0 settings but some directives were renamed and new directives were added.

Enabling mod_perl

To enable mod_perl built as DSO add to httpd.conf:

  LoadModule perl_module modules/

This setting specifies the location of the mod_perl module relative to the ServerRoot setting, therefore you should put it somewhere after ServerRoot is specified.

If mod_perl has been statically linked it's automatically enabled.

For Win32 specific details, see the documentation on Win32 configuration.

Remember that you can't use mod_perl until you have configured Apache to use it. You need to configure Registry scripts or custom handlers.

Server Configuration Directives

<Perl> Sections

With <Perl>...</Perl> sections, it is possible to configure your server entirely in Perl.

Please refer to the Apache2::PerlSections manpage for more information.

META: a dedicated chapter with examples?

See also: this directive argument types and allowed location.

=pod, =over and =cut

It's known that anything written between tokens =pod and =cut is ignored by the Perl parser. mod_perl allows you to use the same technique to make Apache ignore things in httpd.conf (similar to # comments). With an exception to =over apache and =over httpd sections which are visible to Apache.

For example the following configuration:

  #file: httpd.conf



  PerlSetVar A 1


  =over apache


  PerlSetVar B 2




  PerlSetVar C 3




  PerlSetVar D 4

Apache will see:

  PerlSetVar B 2

  PerlSetVar D 4

but not:

  PerlSetVar A 1

  PerlSetVar C 3

=over httpd is just an alias to =over apache. Remember that =over requires a corresponding =back.


PerlAddVar is useful if you need to pass in multiple values into the same variable emulating arrays and hashes. For example:

   PerlAddVar foo bar 

   PerlAddVar foo bar1

   PerlAddVar foo bar2


You would retrieve these values with:

  my @foos = $r->dir_config('foo');

This would fill the @foos array with 'bar', 'bar1', and 'bar2'.

To pass in hashed values you need to ensure that you use an even number of directives per key. For example:

  PerlAddVar foo key1

  PerlAddVar foo value1

  PerlAddVar foo key2

  PerlAddVar foo value2

You can then retrieve these values with:

  my %foos = $r->dir_config('foo');

Where %foos will have a structure like:

  %foos = ( 

        key1   => 'value1',

        key2   => 'value2',


See also: this directive argument types and allowed location.


PerlConfigRequire does the same thing as PerlPostConfigRequire|/C_PerlPostConfigRequire_, but it is executed as soon as it is encountered, i.e. during the configuration phase.

You should be using this directive to load only files that introduce new configuration directives, used later in the configuration file. For any other purposes (like preloading modules) use PerlPostConfigRequire|/C_PerlPostConfigRequire_.

One of the reasons for avoding using the PerlConfigRequire directive, is that the STDERR stream is not available during the restart phase, therefore the errors will be not reported. It is not a bug in mod_perl but an Apache limitation. Use PerlPostConfigRequire|/C_PerlPostConfigRequire_ if you can, and there you have the STDERR stream sent to the error_log file (by default).

See also: this directive argument types and allowed location.


The PerlLoadModule directive is similar to PerlModule|/C_PerlModule_, in a sense that it loads a module. The difference is that it's used to triggers an early Perl startup. This can be useful for modules that need to be loaded early, as is the case for modules that implement new Apache directives, which are needed during the configuration phase.

See also: this directive argument types and allowed location.


  PerlModule Foo::Bar

is equivalent to Perl's:

  require Foo::Bar;

PerlModule is used to load modules using their package names.

You can pass one or more module names as arguments to PerlModule:

    PerlModule Apache::DBI CGI DBD::Mysql

Notice, that normally, the Perl startup is delayed until after the configuration phase.

See also: PerlRequire|/C_PerlRequire_.

See also: this directive argument types and allowed location.


The directive PerlOptions provides fine-grained configuration for what were compile-time only options in the first mod_perl generation. It also provides control over what class of Perl interpreter pool is used for a <VirtualHost> or location configured with <Location>, <Directory>, etc.

$r->is_perl_option_enabled($option) and $s->is_perl_option_enabled($option) can be used at run-time to check whether a certain $option has been enabled. (META: probably need to add/move this to the coding chapter)

Options are enabled by prepending + and disabled with -.

See also: this directive argument types and allowed location.

The available options are:


On by default, can be used to disable mod_perl for a given VirtualHost. For example:

  <VirtualHost ...>

      PerlOptions -Enable



Share the parent Perl interpreter, but give the VirtualHost its own interpreter pool. For example should you wish to fine tune interpreter pools for a given virtual host:

  <VirtualHost ...>

      PerlOptions +Clone

      PerlInterpStart 2

      PerlInterpMax 2


This might be worthwhile in the case where certain hosts have their own sets of large-ish modules, used only in each host. By tuning each host to have its own pool, that host will continue to reuse the Perl allocations in their specific modules.


Off by default, can be used to have a VirtualHost inherit the value of the PerlSwitches from the parent server.

For instance, when cloning a Perl interpreter, to inherit the base Perl interpreter's PerlSwitches use:

  <VirtualHost ...>

      PerlOptions +Clone +InheritSwitches




Create a new parent Perl interpreter for the given VirtualHost and give it its own interpreter pool (implies the Clone option).

A common problem with mod_perl 1.0 was the shared namespace between all code within the process. Consider two developers using the same server and each wants to run a different version of a module with the same name. This example will create two parent Perl interpreters, one for each <VirtualHost>, each with its own namespace and pointing to a different paths in @INC:

META: is -Mlib portable? (problems with -Mlib on Darwin/5.6.0?)

  <VirtualHost ...>

      ServerName dev1

      PerlOptions +Parent

      PerlSwitches -Mlib=/home/dev1/lib/perl


  <VirtualHost ...>

      ServerName dev2

      PerlOptions +Parent

      PerlSwitches -Mlib=/home/dev2/lib/perl


Remember that +Parent gives you a completely new Perl interpreters pool, so all your modifications to @INC and preloading of the modules should be done again. Consider using PerlOptions +Clone if you want to inherit from the parent Perl interpreter.

Or even for a given location, for something like ``dirty'' cgi scripts:

  <Location /cgi-bin>

      PerlOptions +Parent

      PerlInterpMaxRequests 1

      PerlInterpStart 1

      PerlInterpMax 1

      PerlResponseHandler ModPerl::Registry


will use a fresh interpreter with its own namespace to handle each request.


Disable Perl*Handlers, all compiled-in handlers are enabled by default. The option name is derived from the Perl*Handler name, by stripping the Perl and Handler parts of the word. So PerlLogHandler becomes Log which can be used to disable PerlLogHandler:

  PerlOptions -Log

Suppose one of the hosts does not want to allow users to configure PerlAuthenHandler, PerlAuthzHandler, PerlAccessHandler and <Perl> sections:

  <VirtualHost ...>

      PerlOptions -Authen -Authz -Access -Sections


Or maybe everything but the response handler:

  <VirtualHost ...>

      PerlOptions None +Response



Resolve Perl*Handlers at startup time, which includes loading the modules from disk if not already loaded.

In mod_perl 1.0, configured Perl*Handlers which are not a fully qualified subroutine names are resolved at request time, loading the handler module from disk if needed. In mod_perl 2.0, configured Perl*Handlers are resolved at startup time. By default, modules are not auto-loaded during startup-time resolution. It is possible to enable this feature with:

  PerlOptions +Autoload

Consider this configuration:

  PerlResponseHandler Apache::Magick

In this case, Apache::Magick is the package name, and the subroutine name will default to handler. If the Apache::Magick module is not already loaded, PerlOptions +Autoload will attempt to pull it in at startup time. With this option enabled you don't have to explicitly load the handler modules. For example you don't need to add:

  PerlModule Apache::Magick

in our example.

Another way to preload only specific modules is to add + when configuring those, for example:

  PerlResponseHandler +Apache::Magick

will automatically preload the Apache::Magick module.


Setup the global $r|docs::2.0::api::Apache2::RequestRec object for use with Apache2->request|docs::2.0::api::Apache2::RequestUtil/C_request_.

This setting is enabled by default during the PerlResponseHandler|docs::2.0::user::handlers::http/PerlResponseHandler phase for sections configured as:

  <Location ...>

      SetHandler perl-script



but is not enabled by default for sections configured as:

  <Location ...>

      SetHandler modperl



And can be disabled with:

  <Location ...>

      SetHandler perl-script

      PerlOptions -GlobalRequest



Notice that if you need the global request object during other phases, you will need to explicitly enable it in the configuration file.

You can also set that global object from the handler code, like so:

  sub handler {

      my $r = shift;




The +GlobalRequest setting is needed for example if you use older versions of to process the incoming request. Starting from version 2.93, optionally accepts $r as an argument to new(), like so:

  sub handler {

      my $r = shift;

      my $q = CGI->new($r);



Remember that inside registry scripts you can always get $r at the beginning of the script, since it gets wrapped inside a subroutine and accepts $r as the first and the only argument. For example:


  use CGI;

  my $r = shift;

  my $q = CGI->new($r);


of course you won't be able to run this under mod_cgi, so you may need to do:


  use CGI;

  my $q = $ENV{MOD_PERL} ? CGI->new(shift @_) : CGI->new();


in order to have the script running under mod_perl and mod_cgi.


Scan output for HTTP headers, same functionality as mod_perl 1.0's PerlSendHeader, but more robust. This option is usually needs to be enabled for registry scripts which send the HTTP header with:

  print "Content-type: text/html\n\n";


Turn on merging of Perl*Handler arrays. For example with a setting:

  PerlFixupHandler Apache2::FixupA


  <Location /inside>

      PerlFixupHandler Apache2::FixupB


a request for /inside only runs Apache2::FixupB (mod_perl 1.0 behavior). But with this configuration:

  PerlFixupHandler Apache2::FixupA


  <Location /inside>

      PerlOptions +MergeHandlers

      PerlFixupHandler Apache2::FixupB


a request for /inside will run both Apache2::FixupA and Apache2::FixupB handlers.


Set up environment variables for each request ala mod_cgi.

When this option is enabled, mod_perl fiddles with the environment to make it appear as if the code is called under the mod_cgi handler. For example, the $ENV{QUERY_STRING} environment variable is initialized with the contents of Apache2::args(), and the value returned by Apache2::server_hostname() is put into $ENV{SERVER_NAME}.

But %ENV population is expensive. Those who have moved to the Perl Apache API no longer need this extra %ENV population, and can gain by disabling it. A code using the module require PerlOptions +SetupEnv because that module relies on a properly populated CGI environment table.

This option is enabled by default for sections configured as:

  <Location ...>

      SetHandler perl-script



Since this option adds an overhead to each request, if you don't need this functionality you can turn it off for a certain section:

  <Location ...>

      SetHandler perl-script

      PerlOptions -SetupEnv



or globally:

  PerlOptions -SetupEnv

  <Location ...>



and then it'll affect the whole server. It can still be enabled for sections that need this functionality.

When this option is disabled you can still read environment variables set by you. For example when you use the following configuration:

  PerlOptions -SetupEnv

  PerlModule ModPerl::Registry

  <Location /perl>

    PerlSetEnv TEST hi

    SetHandler perl-script

    PerlResponseHandler ModPerl::Registry

    Options +ExecCGI


and you issue a request for this script:


  use Data::Dumper;

  my $r = Apache2::RequestUtil->request();


  print Dumper(\%ENV);

you should see something like this:

  $VAR1 = {

            'GATEWAY_INTERFACE' => 'CGI-Perl/1.1',

            'MOD_PERL' => 'mod_perl/2.0.1',

            'PATH' => 'bin:/usr/bin',

            'TEST' => 'hi'


Notice that we have got the value of the environment variable TEST.


PerlPassEnv instructs mod_perl to pass the environment variables you specify to your mod_perl handlers. This is useful if you need to set the same environment variables for your shell as well as mod_perl. For example if you had this in your .bash_profile:

   export ORACLE_HOME=/oracle

And defined the following in your httpd.conf:

   PerlPassEnv ORACLE_HOME

The your mod_perl handlers would have access to the value via the standard Perl mechanism:

  my $oracle_home = $ENV{'ORACLE_HOME'};

See also: this directive argument types and allowed location.


  PerlPostConfigRequire /home/httpd/perl/lib/

is equivalent to Perl's:

  require "/home/httpd/perl/lib/";

A PerlRequire filename argument can be absolute or relative to ServerRoot or a filepath in Perl's @INC.

You can pass one or more filenames as arguments to PerlPostConfigRequire:

    PerlPostConfigRequire path1/ path2/

PerlPostConfigRequire is used to load files with Perl code to be run at the server startup. It's not executed as soon as it is encountered, but as late as possible during the server startup.

Most of the time you should be using this directive. For example to preload some modules or run things at the server startup). Only if you need to load modules that introduce new configuration directives, used later in the configuration file you should use PerlConfigRequire|/C_PerlConfigRequire_.

As with any file with Perl code that gets use()'d or require()'d, it must return a true value. To ensure that this happens don't forget to add 1; at the end of

See also: PerlModule|/C_PerlModule_ and PerlLoadModule|/C_PerlLoadModule_.

See also: this directive argument types and allowed location.


PerlRequire does the same thing as PerlPostConfigRequire|/C_PerlPostConfigRequire_, but you have almost no control of when this code is going to be executed. Therefore you should be using either PerlConfigRequire|/C_PerlConfigRequire_ (executes immediately) or PerlPostConfigRequire|/C_PerlPostConfigRequire_ (executes just before the end of the server startup) instead. Most of the time you want to use the latter.

See also: this directive argument types and allowed location.


PerlSetEnv allows you to specify system environment variables and pass them into your mod_perl handlers. These values are then available through the normal perl %ENV mechanisms. For example:

  PerlSetEnv TEMPLATE_PATH /usr/share/templates

would create $ENV{'TEMPLATE_PATH'} and set it to /usr/share/templates.

See also: this directive argument types and allowed location.


PerlSetVar allows you to pass variables into your mod_perl handlers from your httpd.conf. This method is preferable to using PerlSetEnv or Apache's SetEnv and PassEnv methods because of the overhead of having to populate %ENV for each request. An example of how this can be used is:

    PerlSetVar foo bar

To retrieve the value of that variable in your Perl code you would use:

    my $foo = $r->dir_config('foo');

In this example $foo would then hold the value 'bar'. NOTE: that these directives are parsed at request time which is a slower method than using custom Apache configuration directives

See also: this directive argument types and allowed location.


Now you can pass any Perl's command line switches in httpd.conf using the PerlSwitches directive. For example to enable warnings and Taint checking add:

  PerlSwitches -wT

As an alternative to using use lib in to adjust @INC, now you can use the command line switch -I to do that:

  PerlSwitches -I/home/stas/modperl

You could also use -Mlib=/home/stas/modperl which is the exact equivalent as use lib, but it's broken on certain platforms/version (e.g. Darwin/5.6.0). use lib is removing duplicated entries, whereas -I does not.

See also: this directive argument types and allowed location.


mod_perl 2.0 provides two types of SetHandler handlers: modperl and perl-script. The SetHandler directive is only relevant for response phase handlers. It doesn't affect other phases.

See also: this directive argument types and allowed location.


Configured as:

  SetHandler modperl

The bare mod_perl handler type, which just calls the Perl*Handler's callback function. If you don't need the features provided by the perl-script handler, with the modperl handler, you can gain even more performance. (This handler isn't available in mod_perl 1.0.)

Unless the Perl*Handler callback, running under the modperl handler, is configured with:

  PerlOptions +SetupEnv

or calls:


in a void context with no arguments (which has the same effect as PerlOptions +SetupEnv for the handler that called it), only the following environment variables are accessible via %ENV:


  • PATH and TZ (if you had them defined in the shell or httpd.conf)

Therefore if you don't want to add the overhead of populating %ENV, when you simply want to pass some configuration variables from httpd.conf, consider using PerlSetVar and PerlAddVar instead of PerlSetEnv and PerlPassEnv. In your code you can retrieve the values using the dir_config() method. For example if you set in httpd.conf:

  <Location /print_env2>

      SetHandler modperl

      PerlResponseHandler Apache2::VarTest

      PerlSetVar VarTest VarTestValue


this value can be retrieved inside Apache2::VarTest::handler() with:


Alternatively use the Apache core directives SetEnv and PassEnv, which always populate r->subprocess_env, but this doesn't happen until the Apache fixups phase, which could be too late for your needs.

Notice also that this handler does not reset %ENV after each request's response phase, so if one response handler has changed %ENV without localizing the change, it'll affect other handlers running after it as well.


Configured as:

  SetHandler perl-script

Most mod_perl handlers use the perl-script handler. Among other things it does:

  • PerlOptions +GlobalRequest is in effect only during the PerlResponseHandler phase unless:
      PerlOptions -GlobalRequest

    is specified.

  • PerlOptions +SetupEnv is in effect unless:
      PerlOptions -SetupEnv

    is specified.

  • STDIN and STDOUT get tied to the request object $r, which makes possible to read from STDIN and print directly to STDOUT via CORE::print(), instead of implicit calls like $r->puts().

  • Several special global Perl variables are saved before the response handler is called and restored afterwards (similar to mod_perl 1.0). This includes: %ENV, @INC, $/, STDOUT's $| and END blocks array (PL_endav).

  • Entries added to %ENV are passed on to the subprocess_env table, and are thus accessible via r->subprocess_env during the later PerlLogHandler and PerlCleanupHandler phases.


Let's demonstrate the differences between the modperl and the perl-script core handlers in the following example, which represents a simple mod_perl response handler which prints out the environment variables as seen by it:



  package MyApache2::PrintEnv1;

  use strict;


  use Apache2::RequestRec (); # for $r->content_type

  use Apache2::RequestIO ();  # for print

  use Apache2::Const -compile => ':common';


  sub handler {

      my $r = shift;



      for (sort keys %ENV){

          print "$_ => $ENV{$_}\n";



      return Apache2::Const::OK;




This is the required configuration:

  PerlModule MyApache2::PrintEnv1

  <Location /print_env1>

      SetHandler perl-script

      PerlResponseHandler MyApache2::PrintEnv1


Now issue a request to http://localhost/print_env1 and you should see all the environment variables printed out.

Here is the same response handler, adjusted to work with the modperl core handler:



  package MyApache2::PrintEnv2;

  use strict;


  use Apache2::RequestRec (); # for $r->content_type

  use Apache2::RequestIO ();  # for $r->print


  use Apache2::Const -compile => ':common';


  sub handler {

      my $r = shift;




      for (sort keys %ENV){

          $r->print("$_ => $ENV{$_}\n");



      return Apache2::Const::OK;




The configuration now will look as:

  PerlModule MyApache2::PrintEnv2

  <Location /print_env2>

      SetHandler modperl

      PerlResponseHandler MyApache2::PrintEnv2


MyApache2::PrintEnv2 cannot use print() and therefore uses $r->print() to generate a response. Under the modperl core handler %ENV is not populated by default, therefore subprocess_env() is called in a void context. Alternatively we could configure this section to do:

    PerlOptions +SetupEnv

If you issue a request to http://localhost/print_env2, you should see all the environment variables printed out as with http://localhost/print_env1.

Server Life Cycle Handlers Directives

See Server life cycle.


See PerlOpenLogsHandler|docs::2.0::user::handlers::server/C_PerlOpenLogsHandler_.


See PerlPostConfigHandler|docs::2.0::user::handlers::server/C_PerlPostConfigHandler_.


See PerlChildInitHandler|docs::2.0::user::handlers::server/C_PerlChildInitHandler_.


See PerlChildExitHandler|docs::2.0::user::handlers::server/C_PerlChildExitHandler_.

Protocol Handlers Directives

See Protocol handlers.


See PerlPreConnectionHandler|docs::2.0::user::handlers::protocols/PerlPreConnectionHandler.


See PerlProcessConnectionHandler|docs::2.0::user::handlers::protocols/PerlProcessConnectionHandler.

Filter Handlers Directives

mod_perl filters are described in the filter handlers tutorial, Apache2::Filter|docs::2.0::api::Apache2::Filter and Apache2::FilterRec|docs::2.0::api::Apache2::FilterRec manpages.

The following filter handler configuration directives are available:


See PerlInputFilterHandler|docs::2.0::user::handlers::filters/C_PerlInputFilterHandler_.


See PerlOutputFilterHandler|docs::2.0::user::handlers::filters/C_PerlOutputFilterHandler_.


See PerlSetInputFilter|docs::2.0::user::handlers::filters/C_PerlSetInputFilter_.


See PerlSetInputFilter|docs::2.0::user::handlers::filters/C_PerlSetInputFilter_.

HTTP Protocol Handlers Directives

See HTTP protocol handlers.


See PerlPostReadRequestHandler|docs::2.0::user::handlers::http/PerlPostReadRequestHandler.


See PerlTransHandler|docs::2.0::user::handlers::http/PerlTransHandler.


See PerlMapToStorageHandler|docs::2.0::user::handlers::http/PerlMapToStorageHandler.


See PerlInitHandler|docs::2.0::user::handlers::http/PerlInitHandler.


See PerlHeaderParserHandler|docs::2.0::user::handlers::http/PerlHeaderParserHandler.


See PerlAccessHandler|docs::2.0::user::handlers::http/PerlAccessHandler.


See PerlAuthenHandler|docs::2.0::user::handlers::http/PerlAuthenHandler.


See PerlAuthzHandler|docs::2.0::user::handlers::http/PerlAuthzHandler.


See PerlTypeHandler|docs::2.0::user::handlers::http/PerlTypeHandler.


See PerlFixupHandler|docs::2.0::user::handlers::http/PerlFixupHandler.


See PerlResponseHandler|docs::2.0::user::handlers::http/PerlResponseHandler.


See PerlLogHandler|docs::2.0::user::handlers::http/PerlLogHandler.


See PerlCleanupHandler|docs::2.0::user::handlers::http/PerlCleanupHandler.

Threads Mode Specific Directives

These directives are enabled only in a threaded mod_perl+Apache combo:


The number of interpreters to clone at startup time.

Default value: 3

See also: this directive argument types and allowed location.


If all running interpreters are in use, mod_perl will clone new interpreters to handle the request, up until this number of interpreters is reached. when PerlInterpMax is reached, mod_perl will block (via COND_WAIT()) until one becomes available (signaled via COND_SIGNAL()).

Default value: 5

See also: this directive argument types and allowed location.


The minimum number of available interpreters this parameter will clone interpreters up to PerlInterpMax, before a request comes in.

Default value: 3

See also: this directive argument types and allowed location.


mod_perl will throttle down the number of interpreters to this number as those in use become available.

Default value: 3


The maximum number of requests an interpreter should serve, the interpreter is destroyed when the number is reached and replaced with a fresh clone.

Default value: 2000

See also: this directive argument types and allowed location.


As mentioned, when a request in a threaded mpm is handled by mod_perl, an interpreter must be pulled from the interpreter pool. The interpreter is then only available to the thread that selected it, until it is released back into the interpreter pool. By default, an interpreter will be held for the lifetime of the request, equivalent to this configuration:

  PerlInterpScope request

For example, if a PerlAccessHandler is configured, an interpreter will be selected before it is run and not released until after the logging phase.

Interpreters will be shared across sub-requests by default, however, it is possible to configure the interpreter scope to be per-sub-request on a per-directory basis:

  PerlInterpScope subrequest

With this configuration, an autoindex generated page, for example, would select an interpreter for each item in the listing that is configured with a Perl*Handler.

It is also possible to configure the scope to be per-handler:

  PerlInterpScope handler

For example if PerlAccessHandler is configured, an interpreter will be selected before running the handler, and put back immediately afterwards, before Apache moves onto the next phase. If a PerlFixupHandler is configured further down the chain, another interpreter will be selected and again put back afterwards, before PerlResponseHandler is run.

For protocol handlers, the interpreter is held for the lifetime of the connection. However, a C protocol module might hook into mod_perl (e.g. mod_ftp) and provide a request_rec record. In this case, the default scope is that of the request. Should a mod_perl handler want to maintain state for the lifetime of an ftp connection, it is possible to do so on a per-virtualhost basis:

  PerlInterpScope connection

Default value: request

See also: this directive argument types and allowed location.

Debug Directives


The PerlTrace is used for tracing the mod_perl execution. This directive is enabled when mod_perl is compiled with the MP_TRACE=1 option.

To enable tracing, add to httpd.conf:

  PerlTrace [level]

where level is either:


which sets maximum logging and debugging levels;

a combination of one or more option letters from the following list:

  a Apache API interaction

  c configuration for directive handlers

  d directive processing

  f filters

  e environment variables

  g globals management

  h handlers

  i interpreter pool management

  m memory allocations

  o I/O

  r Perl runtime interaction

  s Perl sections

  t benchmark-ish timings

Tracing options add to the previous setting and don't override it. So for example:

   PerlTrace c


   PerlTrace f

will set tracing level first to 'c' and later to 'cf'. If you wish to override settings, unset any previous setting by assigning 0 (zero), like so:

   PerlTrace c


   PerlTrace 0

   PerlTrace f

now the tracing level is set only to 'f'. You can't mix the number 0 with letters, it must be alone.

When PerlTrace is not specified, the tracing level will be set to the value of the $ENV{MOD_PERL_TRACE} environment variable.

See also: this directive argument types and allowed location.

mod_perl Directives Argument Types and Allowed Location

The following table shows where in the configuration files mod_perl configuration directives are allowed to appear, what kind and how many arguments they expect:

General directives:

    Directive                 Arguments  Scope


  PerlSwitches                 ITERATE    SRV

  PerlRequire                  ITERATE    SRV

  PerlConfigRequire            ITERATE    SRV

  PerlPostConfigRequire        ITERATE    SRC

  PerlModule                   ITERATE    SRV

  PerlLoadModule               RAW_ARGS   SRV

  PerlOptions                  ITERATE    DIR

  PerlSetVar                   TAKE2      DIR

  PerlAddVar                   ITERATE2   DIR

  PerlSetEnv                   TAKE2      DIR

  PerlPassEnv                  TAKE1      SRV

  <Perl> Sections              RAW_ARGS   SRV

  PerlTrace                    TAKE1      SRV

Handler assignment directives:

    Directive                 Arguments  Scope


  PerlOpenLogsHandler          ITERATE    SRV

  PerlPostConfigHandler        ITERATE    SRV

  PerlChildInitHandler         ITERATE    SRV

  PerlChildExitHandler         ITERATE    SRV

  PerlPreConnectionHandler     ITERATE    SRV

  PerlProcessConnectionHandler ITERATE    SRV


  PerlPostReadRequestHandler   ITERATE    SRV

  PerlTransHandler             ITERATE    SRV

  PerlMapToStorageHandler      ITERATE    SRV

  PerlInitHandler              ITERATE    DIR

  PerlHeaderParserHandler      ITERATE    DIR

  PerlAccessHandler            ITERATE    DIR

  PerlAuthenHandler            ITERATE    DIR

  PerlAuthzHandler             ITERATE    DIR

  PerlTypeHandler              ITERATE    DIR

  PerlFixupHandler             ITERATE    DIR

  PerlResponseHandler          ITERATE    DIR

  PerlLogHandler               ITERATE    DIR

  PerlCleanupHandler           ITERATE    DIR


  PerlInputFilterHandler       ITERATE    DIR

  PerlOutputFilterHandler      ITERATE    DIR

  PerlSetInputFilter           ITERATE    DIR

  PerlSetOutputFilter          ITERATE    DIR

Perl Interpreter management directives:

    Directive                 Arguments  Scope


  PerlInterpStart              TAKE1      SRV

  PerlInterpMax                TAKE1      SRV

  PerlInterpMinSpare           TAKE1      SRV

  PerlInterpMaxSpare           TAKE1      SRV

  PerlInterpMaxRequests        TAKE1      SRV

  PerlInterpScope              TAKE1      DIR

mod_perl 1.0 back-compatibility directives:

    Directive                 Arguments  Scope


  PerlHandler                   ITERATE   DIR

  PerlSendHeader                FLAG      DIR

  PerlSetupEnv                  FLAG      DIR

  PerlTaintCheck                FLAG      SRV

  PerlWarn                      FLAG      SRV

The Arguments column represents the type of arguments directives accepts, where:

Expects a list of arguments.

Expects one argument, followed by at least one or more arguments.

Expects one argument only.

Expects two arguments only.

One of On or Off (case insensitive).

The function parses the command line by itself.

The Scope column shows the location the directives are allowed to appear in:

Global configuration and <VirtualHost> (mnemonic: SeRVer). These directives are defined as RSRC_CONF in the source code.

<Directory>, <Location>, <Files> and all their regular expression variants (mnemonic: DIRectory). These directives can also appear in .htaccess files. These directives are defined as OR_ALL in the source code.

These directives can also appear in the global server configuration and <VirtualHost>.

Apache specifies other allowed location types which are currently not used by the core mod_perl directives and their definition can be found in include/httpd_config.h (hint: search for RSRC_CONF).

Also see Stacked Handlers.

Server Startup Options Retrieval

Inside httpd.conf one can do conditional configuration based on the define options passed at the server startup. For example:

  <IfDefine PERLDB>


          use Apache::DB ();




      <Location />

          PerlFixupHandler Apache::DB



So only when the server is started as:

  % httpd C<-DPERLDB> ...

The configuration inside IfDefine will have an effect. If you want to have some configuration section to have an effect if a certain define wasn't defined use !, for example here is the opposite of the previous example:

  <IfDefine !PERLDB>

      # ...


If you need to access any of the startup defines in the Perl code you use Apache2::ServerUtil::exists_config_define()|docs::2.0::api::Apache2::ServerUtil/C_exists_config_define_. For example in a startup file you can say:

  use Apache2::ServerUtil ();

  if (Apache2::ServerUtil::exists_config_define("PERLDB")) {

      require Apache::DB;



For example to check whether the server has been started in a single mode use:

  if (Apache2::ServerUtil::exists_config_define("ONE_PROCESS")) {

      print "Running in a single mode";


MODPERL2 Define Option

When running under mod_perl 2.0 a special configuration ``define'' symbol MODPERL2 is enabled internally, as if the server had been started with -DMODPERL2. For example this can be used to write a configuration file which needs to do something different whether it's running under mod_perl 1.0 or 2.0:

  <IfDefine MODPERL2>

      # 2.0 configuration


  <IfDefine !MODPERL2>

      # else


From within Perl code this can be tested with Apache2::ServerUtil::exists_config_define()|docs::2.0::Apache2::ServerUtil/C_exists_config_define_, for example:

  use Apache2::ServerUtil ();

  if (Apache2::ServerUtil::exists_config_define("MODPERL2")) {

      # some 2.0 specific code


Perl Interface to the Apache Configuration Tree

For now refer to the Apache2::Directive manpage and the test t/response/TestApache2/ in the mod_perl source distribution.

META: need help to write the tutorial section on this with examples.

Adjusting @INC

You can always adjust contents of @INC before the server starts. There are several ways to do that.

  • In the startup file you can use the lib pragma like so:
      use lib qw(/home/httpd/project1/lib /tmp/lib);
      use lib qw(/home/httpd/project2/lib);

  • httpd.conf
  • In httpd.conf you can use the PerlSwitches directive to pass arguments to perl as you do from the command line, e.g.:
      PerlSwitches -I/home/httpd/project1/lib -I/tmp/lib
      PerlSwitches -I/home/httpd/project2/lib

PERL5LIB and PERLLIB Environment Variables

The effect of the PERL5LIB and PERLLIB environment variables on @INC is described in the perlrun manpage. mod_perl 2.0 doesn't do anything special about them.

It's important to remind that both PERL5LIB and PERLLIB are ignored when the taint mode (PerlSwitches -T) is in effect. Since you want to make sure that your mod_perl server is running under the taint mode, you can't use the PERL5LIB and PERLLIB environment variables.

However there is the perl5lib module on CPAN, which, if loaded, bypasses perl's security and will affect @INC. Use it only if you know what you are doing.

Modifying @INC on a Per-VirtualHost

If Perl used with mod_perl was built with ithreads support one can specify different @INC values for different VirtualHosts, using a combination of PerlOptions +Parent|/C_Parent_ and PerlSwitches|/C_PerlSwitches_. For example:

  <VirtualHost ...>

      ServerName dev1

      PerlOptions +Parent

      PerlSwitches -I/home/dev1/lib/perl


  <VirtualHost ...>

      ServerName dev2

      PerlOptions +Parent

      PerlSwitches -I/home/dev2/lib/perl


This technique works under any MPM with ithreads-enabled perl. It's just that under prefork your procs will be huge, because you will build a pool of interpreters in each process. While the same happens under threaded mpm, there you have many threads per process, so you need just 1 or 2 procs and therefore less memory will be used.

General Issues


Maintainer is the person(s) you should contact with updates, corrections and patches.

  • Stas Bekman <stas (at)>


  • Doug MacEachern <dougm (at)>

  • Stas Bekman <stas (at)>

Only the major authors are listed above. For contributors see the Changes file.