Help-Site Computer Manuals
Software
Hardware
Programming
Networking
  Algorithms & Data Structures   Programming Languages   Revision Control
  Protocols
  Cameras   Computers   Displays   Keyboards & Mice   Motherboards   Networking   Printers & Scanners   Storage
  Windows   Linux & Unix   Mac

strict
Perl pragma to restrict unsafe constructs

strict - Perl pragma to restrict unsafe constructs


NAME

strict - Perl pragma to restrict unsafe constructs


SYNOPSIS


    use strict;

    use strict "vars";

    use strict "refs";

    use strict "subs";

    use strict;

    no strict "vars";


DESCRIPTION

If no import list is supplied, all possible restrictions are assumed. (This is the safest mode to operate in, but is sometimes too strict for casual programming.) Currently, there are three possible things to be strict about: ``subs'', ``vars'', and ``refs''.

strict refs
This generates a runtime error if you use symbolic references (see perlref).

    use strict 'refs';

    $ref = \$foo;

    print $$ref;        # ok

    $ref = "foo";

    print $$ref;        # runtime error; normally ok

    $file = "STDOUT";

    print $file "Hi!";  # error; note: no comma after $file

There is one exception to this rule:


    $bar = \&{'foo'};

    &$bar;

is allowed so that goto &$AUTOLOAD would not break under stricture.

strict vars
This generates a compile-time error if you access a variable that wasn't declared via ``our'' or use vars, localized via my(), or wasn't fully qualified. Because this is to avoid variable suicide problems and subtle dynamic scoping issues, a merely local() variable isn't good enough. See perlfunc/my and perlfunc/local.

    use strict 'vars';

    $X::foo = 1;         # ok, fully qualified

    my $foo = 10;        # ok, my() var

    local $foo = 9;      # blows up

    package Cinna;

    our $bar;                   # Declares $bar in current package

    $bar = 'HgS';               # ok, global declared via pragma

The local() generated a compile-time error because you just touched a global name without fully qualifying it.

Because of their special use by sort(), the variables $a and $b are exempted from this check.

strict subs
This disables the poetry optimization, generating a compile-time error if you try to use a bareword identifier that's not a subroutine, unless it appears in curly braces or on the left hand side of the ``=>'' symbol.

    use strict 'subs';

    $SIG{PIPE} = Plumber;       # blows up

    $SIG{PIPE} = "Plumber";     # just fine: bareword in curlies always ok

    $SIG{PIPE} = \&Plumber;     # preferred form

See perlmodlib/Pragmatic Modules.

Programminig
Wy
Wy
yW
Wy
Programming
Wy
Wy
Wy
Wy