Aijin!

I would follow runrigs lead. It's flexible and straight forward, and makes it easy to pass multiple arguments to sub_to_pass and the interface is consistent with fun things like  system.

sub sub_to_receive {
# Example usage
# sub_to_receive('123', \&sub_to_be_passed, 'arg');
# sub_to_receive('123', \&sub_to_be_passed, 'arg1', 'arg2');
# sub_to_receive('123', \&sub_to_be_passed, @args);
#

  my ($x, $sub_to_run, @args) = @_;
  $sub_to_run->(@args, "lalala");

}
[download]

--
Clayton aka "Tex"