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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 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 strict vars-
This generates a compile-time error if you access a variable that wasn't declared via "our" or
use vars, localized viamy(), or wasn't fully qualified. Because this is to avoid variable suicide problems and subtle dynamic scoping issues, a merelylocal()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.
File path = /ww/webwork/pg/lib/ww_strict.pm
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