What perl are you using? Those should be identical at runtime, since interpolation is converted to concatenation by the tokenizer. For evidence, try: 
% perl -MO=Deparse -e '$foo=q(foo)'
$foo = 'foo';
-e syntax OK
% perl -MO=Deparse -e '$foo=qq(foo)'
$foo = 'foo';
-e syntax OK

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I ran your benchmark program, and got +/- 3%. Try running it a few times.

In reply to Re: Re: Idiomatic optimizations by sfink
in thread Idiomatic optimizations by Juerd

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