Regex to capture an optional group in the middle of a block of input

Question

I\'m stuck on a RegEx problem that\'s seemingly very simple and yet I can\'t get it working.

Suppose I have input like this:

Some text %interestingbi         


        

Answer 1

Why do you have the extra set of parentheses?

Try this:

%interestingbit%.+?(?OPTIONAL_THING)?.+?%anotherinterestingbit%

Or maybe this will work:

%interestingbit%.+?(?OPTIONAL_THING|).+?%anotherinterestingbit%

In this example, the group captures OPTIONAL_THING, or nothing.