Ergh.

Test code that I used had the module name in double quotes instead of single quotes. Man, gotta quit programming when I'm so tired. I noticed later that my mistake wasn't interpolated vs. uninterpolated strings, but was the fact that I was trying to dereference a scalar (via $$ notation), rather than just using the value of the scalar in place of a module name.

Thanks for the fix on my bonehead mistake.