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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 the perlref manpage).

               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


     `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 the my entry in the
           perlfunc manpage and the local entry in the perlfunc
           manpage.

               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 the Pragmatic Modules entry in the perlmodlib manpage.









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Created 1996-2024 by Maxim Chirkov

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