Profilers for Bro

Hai,
Currently I'm on analysis of pattern matching of Bro ids s/w. I came across
several files such as RE.cc, RuleMatcher.cc, PIA.cc etc. But at this point I
can't corelate them. Can anybody help out with the pattern matching in Bro.
I shall be much obliged to you even if you send me some documents regarding
pattern matching in Bro.
Thank you,
Abin C. M.