I love how much smarter you are than me and that dummy claude
choroba! I have a bad habit of avoiding // because it can give me an extra 10 years of backwards compatibility, just in case anyone is still using anything older than v5.10.0. As you've seen, this probably poor decision, makes zero the bane of my existence; but it was a fun minute-long puzzle to fix the bug:
my $f = defined $_[0] ? shift : return;