With Perl 5.6 you can use 'use re "debug"' and will get something like a trace of the regex.
It's not easy to read, but it helps.
I think you must have perl compiled with the DEBUGGING flag.

Look at perldoc perldebguts and search for 'regular'.

In reply to Re: Debugging regular expressions by busunsl
in thread Debugging regular expressions by larsen

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