The problem lies in the word "file", where "fi" can be represented by a ligature. Adding single /a doesn't help, but /aa solves the problem. So, if you don't work with unicode, you can just run your scripts like
Unbelievable :) I would have never thought about that one! Thank you so much.
Then there is less code to modify than I thought so I can probably modify these very specific regexps.