plpgsql support

hello sir,

 I have written a function. The language used is sql. I am not getting erro=
r if I assign an alias to a variable or if I try to declare any of the vari=
able.
I could figure out that I require support if plpgsql, but I am not able to =
get the suppor of this language. I have tried

CREATE PROCEDURAL LANGUAGE 'plpgsql'=20
HANDLER plpgsql_call_handler=20
LANCOMPILER 'PL/PGSQL'


I have even tried
CREATE LANGUAGE 'plpgsql'

But I am not able to set it. What is that I should do to set up this langua=
ge support.

Regards
nagesh