"In Postgres, one and the same function name can be used for different functions as long as the number of arguments or their types differ. This would collide with Tcl procedure names. To offer the same flexibility in PL/Tcl, the internal Tcl procedure names contain the object ID of the procedures pg_proc row as part of their name. Thus, different argtype versions of the same Postgres function are different for Tcl too."
But I still don't know the solution. I've tried [oid]_[proname], [oid][proname], [proname][oid], [proname]_[oid] and none of these work.