use vars

use vars qw($frobbed @munge %seen);

This pragma, once used to declare a global variable, is now somewhat deprecated in favor of the our modifier. The previous declaration is better accomplished using:

our($frobbed, @munge, %seen);
or even:
our $frobbed = "F"; our @munge = "A" .. $frobbed; our %seen = ();
No matter which of these you use, remember that they're talking about package globals, not file-scoped lexicals.