http://www.perlmonks.org?node_id=1101778


in reply to Re^5: Turning on regexp debugging at runtime
in thread Turning on regexp debugging at runtime

This technique was completely new to me as well, but judging from the example code it looks like you can test for pretty much any condition you like if an environment variable doesn't suit your needs.

-- FloydATC

Time flies when you don't know what you're doing