It's not the chained maps that are problematic. It's the magic use of uc buried in the arguments to split, coupled with the use of map EXPR, ARRAY instead of map {...} ARRAY

Personally, I'd prefer to see:

  return map { split / /, uc $_, 2 } @somearray
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I could argue both sides on the explicit return, but I come down in favour of being explicit because you're producing what Kent Beck calls an 'interesting return value'. The use of a block rather than a simple expression clues the reader in to the fact that the call to split isn't as simple as it looks. The explicit $_ argument to uc is there for clarification too.

Frankly, I don't care about the maintainance programmer who's going to be here when I leave, I'm more worried about the psychopath who knows where I live. By paying the price of a few extra characters I get code that I know I won't be scratching my head over tomorrow, and that's the kind of peace of mind I like.

But, if you want to play golf, map{split/ /,uc,2}@somearray looks like a winner.