Not sure this is the right list to vent about this but here you go:
I) select regexp_replace('BEFORE.AFTER','(.*)\..*','\1','g') "Substring"
II) select regexp_replace('BEFORE.AFTER','(.*)\\..*','\\1','g') "Substring"
Executing (II) against pg 8.4.4 or 9.0.4 yields 'BEFORE', but in order for
9.1.7 to yield the same one has to execute (I) .. bummer
-ar