regular expression searches

I am trying to create a PL/PGSQL function that can parse a street address
into the component parts (i.e. "200 W 54th Street" into num->200 dir->W
street->54th type->ST).

What I would like is to be able to use regular expressions within PL/PGSQL
to accomplish this using mapping tables for the different components.

For example, I would have a table with all the different acceptible road
types:
Abbreviation 	| 	Regex
__________________________________
RD			|	R(OA)?D
AV			|	AVE?(NUE)?
ST			| 	STR?(EET)?

and replace everything that matches the regex with the abbreviation while
saving the road type as a variable.

Any help would be appreciated.

Thanks,
David