in reply to adding rank to a match in while loop.

It looks like you're just misusing the do BLOCK while EXPR structure. I think you just need to say while (EXPR) BLOCK and you'll be fine.
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Jeff japhy Pinyan, P.L., P.M., P.O.D, X.S.: Perl, regex, and perl hacker
How can we ever be the sold short or the cheated, we who for every service have long ago been overpaid? ~~ Meister Eckhart