Here’s a regex to find a string in between two strings, that could have any amount of other strings in the mess. This one works well if

• You know the delimiters, ie the two strings that form the boundary of what you’re looking for;
• You know the string you’re looking for in the middle, ie the search term. That’s going to be the one to match.

The regex looks like this

(?=(?!starting-boundary).*ending-boundary)(search-term)

In my case, I was looking for an the string url which was a markup attribute that would only appear between a specific markup tags <action-text-attachment> and </action-text-attachment>. The regex ended up looking like this

(?=(?!action-text-attachment).*<\/action-text-attachment)(url)

Really nifty, this is one of the few times I’ve used a regex that I can imagine using it again in the future.