One way that might shed some light on the source of the problem would be to profile it using Devel::DProf.

If you set the size of the output buffer (PERL_DPROF_BUFFER) to some thing fairly small, say 4K, then that ought to get you fairly close to where the failure occurs.

If, after failure eventually happens (your program will run very slowly), then examining (the quite probably huge output file (TMON.OUT by default) it should not only tell you where it was and what (roughly) it was doing when the failure occurred, but also the sequence of events that led up to it.

I've used this technique to get me much closer to the source of the failure, and give me hints on where to put tracing and/ or set break points. No guarentees that it won't change the point of failure to a completely different place, but even that can be a clue as to the cause.

HTH.

Ps. I am not kidding when I say your program will run slowly! Don;t sit and wait for it to fail. Start it running once you have you coat on and are leaving for the day (or going to bed or whatever). The output will be waiting for you in the morning:). Sitting and watching and waiting will drive you nuts.