pgsql-bugs(at)postgresql(dot)org writes:
> createlang 'plpgsql' test commande don't work
> with output message
> createlang: unsupported language 'plpgsql'
> Supported languages are 'plpgsql', 'pltcl', 'pltclu', and 'plperl'.
Bizarre. Maybe your copy of the createlang script is corrupted somehow?
regards, tom lane