++ Many thanks for this. There's clearly a lot going on under the hood that I wasn't aware of; particularly with respect to "... normally get processed even when not running under -T ...".
More of a curiosity than anything related to tainting; my eye was drawn to the browser tab which appeared to have the emoji for a Bactrian camel (🐫) rather than the usual Dromedary camel (🐪). The text on the tab is very small and I thought that maybe I was miscounting the humps 😕; but no, on checking the source, it appears on two lines:
<title>GitHub - Perl/perl5: 🐫 The Perl programming language</title> <meta name="description" content="🐫 The Perl programming language ...>
I thought this was odd, but then had a vague recollection of there being an O'Reilly ™, ® or © associated with the camel image when used with Perl. After searching through a number of O'Reilly, Perl.com and Perl.org pages, I finally found it in "perl.org - Site Information". Of course, I may be overthinking this; it could just be a typo: � instead of �.
Anyway, back to tainting. I located perl.h — that was very generous of you to void your warranty to help me. :-)
/* By compiling a perl with -DNO_TAINT_SUPPORT or -DSILENT_NO_TAINT_SU +PPORT, * ... * * DANGER! Using NO_TAINT_SUPPORT or SILENT_NO_TAINT_SUPPORT * voids your nonexistent warranty! */
I also looked in the t/ directory for the tests you indicated had failed: run/switcht.t was OK with only 66 lines; op/taint.t was somewhat more daunting with 2,986 lines (I didn't read it all). Realising that there was probably tens of thousands of lines in total, I left it there.