Re: RE greediness

[Anonymous Monk]

The (.*?) in your second attempt is a non-greedy match, which means it will match the smallest possible substring that satisfies the pattern. In this case, it matches an empty string because the optional (?:b=(\w))? can also match the empty string. Use a positive lookahead assertion to ensure that the (.*?) matches up to the optional b=(\w) part, but doesn't include it:

/(a)(?:(.*?)(?:b=(\w)))?/

[choroba]

(?:...) is a non-capturing group, positive lookahead uses (?=...) which I can't find in the regex used.

[Anonymous Monk]

(?:...) is a non-capturing group, positive lookahead uses (?=...) which I can't find in the regex used.
Sorry for the typo, meant to type this, but it's still wrong:

/(a)(?=(.*?)(?:b=(\w)))?/

This seems to work:

/(a)(.*?)(?=b=(\w)|\z)/