create procedure dbo.PerlTest2(
 @id integer = NULL OUTPUT,
 @SomeParam varchar(100)
)
as
begin
 INSERT INTO test (stuff)
 VALUES (@SomeParam)
 SELECT @id = @@IDENTITY
end
go 

Grant Execute on dbo.PerlTest2 to test 
go

sp_procxmode 'PerlTest2', unchained
go