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;
+
+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+[[{].*[]}]$/) {
+ require Carp;
+ Carp::croak("Can't declare individual elements of hash or array");
+ } elsif ($^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}::$sym"}
+ : do {
+ require Carp;
+ Carp::croak("'$ch$sym' is not a valid variable name");
+ });
+ }
+};
+
+1;
+__END__
+
=head1 NAME
vars - Perl pragma to predeclare global variable names
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 to the later-loaded routines.
+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<perlmod/Pragmatic Modules>.
+See L<perlmodlib/Pragmatic Modules>.
=cut
-
-require 5.002;
-use Carp;
-
-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*', $sym);
- *{"${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");
- }
-};
-
-1;