[Streaming] How to pass arguments to a map/reduce script

[Gopal Gandhi]

I am using Hadoop streaming and I need to pass arguments to my map/reduce 
script. Because a map/reduce script is triggered by hadoop, like
hadoop ....  -file MAPPER -mapper "$MAPPER" -file REDUCER -reducer "$REDUCER" 
...
How can I pass arguments to MAPPER?

I tried -cmdenv name=val , but it does not work.
Anybody can help me? Thanks lot.