Stored Proc Parameters in Reporting Services

My users have two kinds of data they need to see in this report, Engineering data, or Production data.  And sometimes both.

In my Reporting Services report, I have a drop down combo box that shows PROD, ENG, and BOTH.

If my user selects ENG I'd like the stored procedure to limit the data:
WHERE Pool IN ('ENG_PM','DEV_RP')

If my user select PROD I would like my stored procedure to limit the data:
WHERE Pool IN ('FAB')

if my user passes BOTH, I'd like to include all of both of those, but nothing else.

So, in my Report, I created a parameter called POOL.  My plan was to have the user see one thing, but pass another.  In other words, have a parameter label (ENG) and a parameter value ('ENG_PM','DEV_RP')

So I got it all set up that way for all three scenarios.

In my stored proc, I added the line:
WHERE pool IN (@Pool)

But now when I run my report, I get zero data.

I'm passing two other parameters (StartDate and EndDate) so I know my parameters are working fine.  (I think I'm just passing something that looks bad when it gets to the other side.  Like maybe it's not OK to pass single quote tick marks, or maybe I need to pass parentheses as well, or something.)

If I could see what SQL statement my stored procedure is trying to run, I could probably figure out how to fix it.  But I'm not sure how to check what is actually being passed by the report (and received by the stored proc.)  Is there a way to see that?

Alternatively, if I knew how, I thought of just passing the word "PROD" (for example) to my Stored Proc and using an IF statement that translates it to the WHERE statement.  But my search of the web isn't showing me that that's a possiblity.  And TSQL isn't my native database language.

Any ideas?