For the final interation, leave the DEBUG blocks always commented out. When you need to debug, simply try this:

perl -e 's/^#(.*)$/$1/ if /\bDEBUG\b/../\bENDDEBUG\b/' foo.pl | perl
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and eliminate the intermediate file. Actually, more likely to reduce the odds I will ship code with the debug blocks still enabled :)

mikfire