No worries, I'm here for over 10 years with thousands of posts and I can't remember seeing a hash slice on an anonymous hash constructed from a map. (good to know it's possible, though)

also the ,=> is highly idiomatic.

I have trouble seeing a justification for this degree of golfing, other than probably (micro) optimization.

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};
[download]

> > this degree of golfing

Cheers Rolf
_{(addicted to the Perl Programming Language :)
Wikisyntax for the Monastery FootballPerl is like chess, only without the dice}