I'd joke about Perl 5 being write-only until I had to go read my own code from only months prior. I would get so mad at myself for making it so hard to follow but then for expediency I'd go and do the same damn thing in the current batch of code. Then months later curse myself. I've opened Perl files that I swear had bitrot but nope, not corruption, just a bunch of sigils and weird operators.
