perldebguts may tell you what you need to know. In purticular, I think you want a DB::sub. I'm in the middle of something else, though, so I don't want to break my concentration to do this. (OTOH, from this quick read of perldebguts, I found something that might be useful for me.)
Warning: Unless otherwise stated, code is untested. Do not use without understanding. Code is posted in the hopes it is useful, but without warranty. All copyrights are relinquished into the public domain unless otherwise stated. I am not an angel. I am capable of error, and err on a fairly regular basis. If I made a mistake, please let me know (such as by replying to this node).