Ah....sorry. Stupid of me.

That does raise an interesting question as to what code a perl optimiser would be allowed to remove. You'd really like the optimiser to be able to nuke code like this:

  while (tight_loop) {
    write_to_log("Some msg involving $somevar") if REALLY_HEAVY_DEBUG;
    some_more_code();
  }
[download]

if the constant evaluated to 0. I guess if $somevar was relevant to the debugging then it would be closed over anyway, but that is a bit too subtle.