source: trunk/third/perl/lib/vars.pm @ 14545

package vars;

require 5.002;

# 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();

sub import {
    my $callpack = caller;
    my ($pack, @imports, $sym, $ch) = @_;
    foreach $sym (@imports) {
        ($ch, $sym) = unpack('a1a*', $sym);
        if ($sym =~ tr/A-Za-z_0-9//c) {
            # time for a more-detailed check-up
            if ($sym =~ /::/) {
                require Carp;
                Carp::croak("Can't declare another package's variables");
            } elsif ($sym =~ /^\w+[[{].*[]}]$/) {
                require Carp;
                Carp::croak("Can't declare individual elements of hash or array");
            } elsif (warnings::enabled() and length($sym) == 1 and $sym !~ tr/a-zA-Z//) {
                warnings::warn("No need to declare built-in vars");
            }
        }
        *{"${callpack}::$sym"} =
          (  $ch eq "\$" ? \$   {"${callpack}::$sym"}
           : $ch eq "\@" ? \@   {"${callpack}::$sym"}
           : $ch eq "\%" ? \%   {"${callpack}::$sym"}
           : $ch eq "\*" ? \*   {"${callpack}::$sym"}
           : $ch eq "\&" ? \&   {"${callpack}::$sym"}
           : do {
                require Carp;
                Carp::croak("'$ch$sym' 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NOTE: The functionality provided by this pragma has been superseded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