It is a custom format.

I've heard that often, but I'll take your word for it :)

The problem is not parsing the file, but finding the dependencies as explained above. Thanks.

I hate to be contrary :) but yes, the problem is parsing.

First you build a data structure (parse), then you walk the data structure looking for dependencies.

If parsing wasn't a problem, surely you would have shared your parser, or at least, the data structure it creates?

Your response to Marshal's node Re: Parsing a file and finding the dependencies in it firmly confirms that parsing was indeed a problem.