Getting Teamsite Userid in DCR

System

Hi,
How can I get the userid in my DCR so I can send it as an argument in my perl script.
Here is an example of what I am trying to do:
<item name="MARKET">
<select required="t">
<inline command="/opt/interwoven/iw-home/iw-
perl/bin/iwperl /opt/interwoven/iw-
home/local/xyz/test.ipl IW_USER"/>
</select>
</item>"

I was hoping IW_USER would contain the userid.
Please tell me what I am doing wrong.

Thanks in advance!