It's a dirty rotten hack but someone had to do it:

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";
   }
}
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/J\