how do I get rid of yaml and such built up cruft, from time to time, during automated testing

[M W487]

Hi.  When I run

$ minismokebox --perl /usr/bin/perl.exe --debug --indices --backend
CPAN::Reporter --reverse > CP_75.txt 2>&1 &

I get output that includes, for example:

"Going to read 4003 yaml files from /home/Administrator/.cpan/build/"

Having so many yaml (and such files and directories) build up seems to
slow down my testing without a large benefit that I can see.

Can someone tell me what are the best ways to avoid or correct
excessive build up?

Thanks.