I have trouble seeing a justification for this degree of golfing,

Perl golf is the art of using as few characters as possible so this doesn't really qualify.

With unnecessary characters removed: 


my@i=grep defined,@{{map{lc,$_}@a}}{map{lc}@b};

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In reply to Re^3: Strange grep construct by jwkrahn
in thread Strange grep construct by mzvk

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