package Foo;
                                                                                
sub bar {};
                                                                                
1;
                                                                                
package Bar;
                                                                                
use base qw(Foo);
                                                                                
1;
                                                                                
package main;
                                                                                
for my $foo (grep /::/ , keys %:: )
{
   if ( exists %{$foo}->{ISA} )
   {
      print @{%{$foo}->{ISA}},"\n";
   }
}