note dchetlin This is a good question. The answer is that the REx engine does <strong>not</strong> optimize <code>\d{2}</code> into <code>\d\d</code>. <p>Here's how to check: <p><code> [~] $ perl -Mre=debug -e'qr/\d{2}/' Freeing REx: `,' Compiling REx `\d{2}' size 4 first at 3 1: CURLY {2,2}(4) 3: DIGIT(0) 4: END(0) stclass `DIGIT' minlen 2 Freeing REx: `\d{2}' [~] $ perl -Mre=debug -e'qr/\d\d/' Freeing REx: `,' Compiling REx `\d\d' size 3 first at 1 1: DIGIT(2) 2: DIGIT(3) 3: END(0) stclass `DIGIT' minlen 2 Freeing REx: `\d\d'</code> <p>Why doesn't it? I don't know. But as the Benchmarks above have noted, I can't imagine that difference being notable enough to really worry about. <p>-dlc 38175 38175