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 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

strict vars
This generates a compile-time error if you access a variable that wasn't 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 and local.

    use strict 'vars';
    $X::foo = 1;	 # ok, fully qualified
    my $foo = 10;	 # ok, my() var
    local $foo = 9;	 # blows up

The local generated a compile-time error because you just touched a global name without fully qualifying it.

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.