How do I make part of a regular expression optional in Ruby?

Question

To match the following:

On Mar 3, 2011 11:05 AM, \"mr person\" 
wrote: 

I have the following regular expression:

/(On.* (?         


        

Answer 1

Others got your answer. This is just an aside re: Regular Expressions.

When you say "conditions" in regular expressions, it refers to the regex language. Like any language, its a branch in code execution, but the code is a different regular expression path, the "code" of regular expressions.

So in psudo code: if (evaluation is true) do this regular sub-expression, else do this other sub-expression.

This conditional exists in advanced regular expression engines ... Perl.
Perl uses the most advanced regular expression engine that exists. In version 6 and beyond it will be an integral part of the language, where code and expression intermingle seamlessly.

Perl 5.10 has this construct:
(?(condition)yes-pattern|no-pattern).

Edit Just a warning that where Perl goes, every other language follows as far as regular expression.