I stand corrected. I added #!/usr/bin/env perl -T to the top of the file and print STDERR ("\n\n\nTaint = '", ${^TAINT}, "'\n\n\n"); down where the first test would be, and sure enough it printed "Taint = 1" on the console. I was under the mistaken impression that "make test" didn't load the .t file directly, but instead ran it in an eval.

Sorry I doubted you!