For the performance, one thing that comes to my mind is the /o qualifier to compile once only

Yikes! Don't ever recommend that. It's rarely needed and causes more trouble than it is worth. Perl already does optimizations for patterns that contain no variables and for patterns that do contain variables that don't vary over the lifetime of the code in which the pattern appears, so /o won't buy you anything there. If you really need the "compile once" idea, just use qr/.../

duff

In reply to Re^2: Analyzing regular expression performance by duff
in thread Analyzing regular expression performance by Sprad

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