Store printf value inside variable?

From: Boo (strum4life_at_hotmail.com)
Date: 03/30/05 

Date: 29 Mar 2005 17:52:54 -0800

Using printf, I can get the output I want:

printf("ch:\t6%u\n",$ch);

The %u allows me to convert a negative value to an unsigned decimal
number.

My problem is that I don't want to output this to the screen. I need
to store it as a variable. Is there any way to do this? Thanks!