strict(3)

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.) Cur
rently, 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 = oo;
print $$ref; # ok
$ref = "foo";
print $$ref; # runtime error; normally ok
$file = "STDOUT";
print $file "Hi!"; # error; note: no comma af

ter $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 quali
fied. Because this is to avoid variable suicide
problems and subtle dynamic scoping issues, a merely
local() variable isn't good enough. See "my" in
perlfunc and "local" in perlfunc.

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 de

clared via pragma

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

Because of their special use by sort(), the vari
ables $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: bare

word in curlies always ok
$SIG{PIPE} = Plumber; # preferred form

See "Pragmatic Modules" in perlmodlib.

perl v5.8.0 2002-06-01 strict(3)