Shot in the dark : Have you tried with two backslashes '\\' ? Because
since you're interpolating $title and have double quotes, it could be
needed to get the regexp string to contain a single backslash.
Also, but why not manage multiple files in /etc/nagios/nrpe.d/ based on
templates instead of managing a single file, since that's much trickier?
Another useless note : You don't need the '.*' at the end of your regexp
if you're not ending it with '$'.
Last useless note : I have also encountered problems with the file_line
'match' parameter, the first one being that the official example is
broken as the 'line' must match the 'match' regexp.
Good luck :-)
Matthias