After a quick look at your code: how about removing comments before processing?

I think that's a must because you do allow comments (in your examples), but then you do when ( /interface/ ) { which will match a commented-out interface line or anything really that mentions the word "interface".

What I usually do for removing comment lines is $line =~ s/#.*$//; next if $line =~ /^\s*$/;

Secondly, if your grammar will grow then you are better off using other solutions, which other Monks I am sure will mention.

bw, bliako