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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.)	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 "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 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 "Pragmatic Modules" in perlmodlib.

Index for Section 3

Alphabetical listing for S

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