use strict;
use warnings;

package Bar;

sub f1 {
 print "there @_\n";
}

package Foo;

for (keys %Bar::) {
 if (exists &{$Bar::{$_}}) {
  no warnings 'redefine';
  my $func = \&{$Bar::{$_}};
  $Bar::{$_} = sub {
     print "hello ";
     goto &$func;
  };
 }
}

package main;

Bar::f1("Bob");