strict - Perl pragma to restrict unsafe constructs
use strict;
use strict "vars";
use strict "refs";
use strict "subs";
use strict;
no strict "vars";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 refsThis 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 $fileThere is one exception to this rule:
$bar = \&{'foo'};
&$bar;is allowed so that goto &$AUTOLOAD would not break under stricture.
strict varsThis 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 "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 declared via pragmaThe 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 subsThis 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