Odd code nit

[p5sagit/p5-mst-13.2.git] / lib / vars.pm

package vars;

require 5.002;

our $VERSION = '1.00';

# The following require can't be removed during maintenance
# releases, sadly, because of the risk of buggy code that does
# require Carp; Carp::croak "..."; without brackets dying
# if Carp hasn't been loaded in earlier compile time. :-(
# We'll let those bugs get found on the development track.
require Carp if $] < 5.00450;

use warnings::register;
require strict;

sub import {
    my $callpack = caller;
    my ($pack, @imports) = @_;
    my ($sym, $ch);
    foreach (@imports) {
        ($ch, $sym) = unpack('a1a*', $_);
	if ($sym =~ tr/A-Za-z_0-9//c) {
	    # time for a more-detailed check-up
	    if ($sym =~ /^\w+[[{].*[]}]$/) {
		require Carp;
		Carp::croak("Can't declare individual elements of hash or array");
	    } elsif (warnings::enabled() and length($sym) == 1 and $sym !~ tr/a-zA-Z//) {
		warnings::warn("No need to declare built-in vars");
            } elsif  ( $^H &= strict::bits('vars') ) {
              Carp::croak("'$_' is not a valid variable name under strict vars");
	    }
	}
	$sym = "${callpack}::$sym" unless $sym =~ /::/;
        *$sym =
          (  $ch eq "\$" ? \$$sym
           : $ch eq "\@" ? \@$sym
           : $ch eq "\%" ? \%$sym
           : $ch eq "\*" ? \*$sym
           : $ch eq "\&" ? \&$sym
           : do {
		require Carp;
		Carp::croak("'$_' is not a valid variable name");
	     });
    }
};

1;
__END__

=head1 NAME

vars - Perl pragma to predeclare global variable names (obsolete)

=head1 SYNOPSIS

    use vars qw($frob @mung %seen);

=head1 DESCRIPTION

NOTE: For variables in the current package, the functionality provided
by this pragma has been superseded by C<our> declarations, available
in Perl v5.6.0 or later.  See L<perlfunc/our>.

This will predeclare all the variables whose names are 
in the list, allowing you to use them under "use strict", and
disabling any typo warnings.

Unlike pragmas that affect the C<$^H> hints variable, the C<use vars> and
C<use subs> declarations are not BLOCK-scoped.  They are thus effective
for the entire file in which they appear.  You may not rescind such
declarations with C<no vars> or C<no subs>.

Packages such as the B<AutoLoader> and B<SelfLoader> that delay
loading of subroutines within packages can create problems with
package lexicals defined using C<my()>. While the B<vars> pragma
cannot duplicate the effect of package lexicals (total transparency
outside of the package), it can act as an acceptable substitute by
pre-declaring global symbols, ensuring their availability to the
later-loaded routines.

See L<perlmodlib/Pragmatic Modules>.

=cut