Okay, I\’m using PERL when I can, because it makes the job. I like how it is not distracting my train of thoughts when tackling a problem and how it makes scripts that are easy to hack later on. I love how it integrated regular expressions, but so far, I wasn\’t fond of how I had to test input patterns one after another with stripped down versions of the regular expression to find why it was failing.
And today I discover use re \’debug\’.
With a simple line, I can get an overview of what the regular expression evaluator is trying to do when parsing a string (coloring added manually).
In yellow, we can track the position within the string: how much has been accepted so far. In green, a quick overview of what was just behind that position and what is just ahead. The blue code seems to identify the next operation that the regexp will do — its program counter, sort of, and in white the detail of what is tried/done.
Bouli's Homebrew Blog 