Constant spinning in Doom

Folks:

If I run "doom" followed by any wad file or none, I get the character's 
viewpoint constantly turning to the left (counterclockwise if viewed 
from above). The doom executable apparently is from the prboom package. 
All the advice I can find has to do with adjusting the sensitivity of 
whatever controllers are connected to the system. This isn't useful.

I'm running this on an Intel i5 PC with a Microsoft mouse. Plain 
vanilla. And in the Doom menus, there doesn't appear to be any choice to 
adjust mouse sensitivity.

Any help would be appreciated, as otherwise all Doom games are unplayable.

Oh, just realized I'm running Debian testing (forky). And for what it's 
worth, I don't recall having this problem with prior versions.

Paul