mm-uu-decode-function is a variable defined in `mm-uu.el'.
Its value is
uudecode-decode-region
This variable may be risky if used as a file-local variable.
Documentation:
*Function to uudecode.
Internal function is done in Lisp by default, therefore decoding may
appear to be horribly slow. You can make Gnus use an external
decoder, such as uudecode.
You can customize this variable.