Octavian,
I do not see how this is possible without modifying the original script at least a little. When you use IO::Tee, you will be able to tie both the LOG and STDOUT to the same filehandle, so that wherever there is a print statement - it will print in both places. By setting auto-flush ($|), you will see events in the log as they happen (or pretty close). The script you write will have to use File::Tail to constantly be checking the bottom of the log looking for a specific event, which will trigger a desired action - such as email/page.

I am not sure how to help beyond this without seeing the code of the original script, some sample output, and what "events" would like a trigger action.

Cheers - L~R