package vars;
-=head1 NAME
+require 5.002;
-vars - Perl pragma to predeclare global variable names
-
-=head1 SYNOPSIS
-
- use vars qw($frob @mung %seen);
-
-=head1 DESCRIPTION
-
-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.
-
-See L<perlmod/Pragmatic Modules>.
-
-=cut
-require 5.000;
-use Carp;
+# 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;
sub import {
my $callpack = caller;
my ($pack, @imports, $sym, $ch) = @_;
foreach $sym (@imports) {
- croak "Can't declare another package's variables" if $sym =~ /::/;
($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+[[{].*[]}]$/) {
+ require Carp;
+ Carp::croak("Can't declare individual elements of hash or array");
+ } elsif ($^W and length($sym) == 1 and $sym !~ tr/a-zA-Z//) {
+ require Carp;
+ Carp::carp("No need to declare built-in vars");
+ }
+ }
*{"${callpack}::$sym"} =
( $ch eq "\$" ? \$ {"${callpack}::$sym"}
: $ch eq "\@" ? \@ {"${callpack}::$sym"}
: $ch eq "\%" ? \% {"${callpack}::$sym"}
: $ch eq "\*" ? \* {"${callpack}::$sym"}
: $ch eq "\&" ? \& {"${callpack}::$sym"}
- : croak "'$ch$sym' is not a valid variable name\n");
+ : do {
+ require Carp;
+ Carp::croak("'$ch$sym' is not a valid variable name");
+ });
}
};
1;
+__END__
+
+=head1 NAME
+
+vars - Perl pragma to predeclare global variable names
+
+=head1 SYNOPSIS
+
+ use vars qw($frob @mung %seen);
+
+=head1 DESCRIPTION
+
+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