Category: regular expressions

Debuggex can turn PCRE regular expressions into railroad diagrams. It’s missing several advanced Perl features, but it’s good for the basic patterns you’ll create in Learning Perl:

Wouldn’t it be great if books had embedded videos? That would make programming textbooks so much easier.

We have to give some hints about how regexes work in the first regex chapter in Learning Perl. It’s hard to describe something like greedy matching and backtracking with only words. It seems like it should be simple to describe, but you are probably like me: you think that because you already understand those concepts. Continue reading “Watch regexes with Regexp::Debugger”

Character class shortcuts used to be easy because ASCII was easy. Either of those were easy if ASCII was what you wanted, but quite limiting otherwise. Perl v5.6 introduced Unicode support and the world started to change.

A good programmer is always trying to eliminate ambiguity. Their code should work the same way everywhere, but character class shortcuts can’t guarantee that anymore. I wrote about these a bit in Know your character classes for The Effective Perler.

Continue reading “The evolution of character class shortcuts”

A student in my Learning Perl class asked about what shows up in a capture when you apply a quantifier to that group. The great thing about computer programming is that you can just try it to find out: Continue reading “Captures with quantifiers match the last captured substring”