This is a fairly common issue I see with Regex. People use . in their regexen when that's not what they actually mean.
In your example you have: /\;(.*?L.*?)\;/. You are looking for a L surrounded by a bunch of stuff that isn't semicolons, but . means "everything", not "everything except semicolons". If you want to say "everything except semicolons" in the regex, then say that: /\;([^;]*?L[^;]*?)\;/
[~]$ perl -le '$_ = ";A-B-C-D;E-F-G-H;J-K-L-M;N-P-R-S;T-W-Y-Z;"; /\;([
+^;]*?L[^;]*?)\;/; print $1;'
tl;dr: Don't use .
if you don't mean .