to analyse a regex, you can use YAPE::Regex::Explain.

update: one example: perl -MYAPE::Regex::Explain -e 'print YAPE::Regex::Explain->new(qr/(<a\s(?:[^>](?!href))*href\s*)(&(&[^;]+;)?(?:.(?!\3))+(?:\3)?)([^>]+>)/)->explain'

For the performance, one thing that comes to my mind is the /o qualifier to compile once only. And if You still suffer from perfomance issues, You might want to use a debugger and/or profiler. But in that case, maybe You should first try to 'divide and conquer' the regexp into a few smaller ones.

In reply to Re: Analyzing regular expression performance by mantadin
in thread Analyzing regular expression performance by Sprad

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