string functions

I have studied the Users Lounge and links off of it, looking for a place
where PG users are sharing extended functions they have created for PG.

In particular I am looking for string functions such as being able to
specify a start point for finding a substring within a string. The existing
PGSQL function position(substring,string) nor strpos(string,substring) have
the option of specifying a start point for the search.

Also I am looking for a function to reverse a string, so that for example
reverse("april") returns "lirpa"

Can anyone point me to an area where users are sharing functions they
created, especially the ones I'm looking for? At this point I'm not able to
write one for myself. I am stuck using Cold Fusion which does include the
functions I need, but is so slow at it that it times out before completing
the update to all of my 250,000 records.

Thank you,

- April