regex_replace problem

Hi folks.

I've got a problem with regex_replace.  As you can see below psql displays the 
error saying the function does not exist.  Can anyone see why, and what I 
need todo to fix it.

Cheers

goole=# select distinct ud_rfl from used_diary where ud_rfl ~ ' *= *'; ud_rfl
-----------12 = 1wk12=1WK12m = 1wk6=1WK
(4 rows)

goole=# select distinct regex_replace(ud_rfl,' *= *','+') from used_diary 
where ud_rfl ~ ' *= *';
ERROR:  function regex_replace(character varying, "unknown", "unknown") does 
not exist
HINT:  No function matches the given name and argument types. You may need to 
add explicit type casts.
goole=# select distinct replace(ud_rfl,'=','+') from used_diary where ud_rfl 
~ ' *= *'; replace
-----------12 + 1wk12+1WK12m + 1wk6+1WK
(4 rows)
[root@stan ~]# rpm -qa|grep postgresql
postgresql-jdbc-8.1.9-1.fc5
postgresql-libs-8.1.9-1.fc5
postgresql-pl-8.1.9-1.fc5
postgresql-contrib-8.1.9-1.fc5
postgresql-server-8.1.9-1.fc5
postgresql-docs-8.1.9-1.fc5
postgresql-python-8.1.9-1.fc5
postgresql-8.1.9-1.fc5
postgresql-test-8.1.9-1.fc5
postgresql-tcl-8.1.9-1.fc5
[root@stan ~]#    
-- 
Gary Stainburn
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