Hello Eily.
Thank you very much for your solution, it seems to be working perfectly after I adapted $pref =~ s/\d++/\\E\\d++\\Q/g; to $pref =~ s/\d++/\\d++/g;
This would have most likely taken me long to figure out, I'm happy I didn't struggle through it for long before asking for help (like I usually would ^^).
Thx again :)