in parallel on a colleague's hunch I'm busy applying the "mt.exe -manifest ExeName.exe.manifest -outputresource:ExeName.exe" line to all perl and pdk executables and dlls.

Actually, I think that could work.

Baring in mind I've never use perlapp and I've only the vaguest notion of what mt.exe actually does.

It seems likely that the manifest checking would not work when you run the distributable .exe resulting from perlapp processing, as (I assume) that is a standalone, all-in-one distributable. It's only when all the bits and pieces of that file are unpacked and decompressed, one of which will be perl.exe and the latter gets run, that the manifest will be checked. Is the right version of perl5x.dll available? Ecetera.

So, theoretically thinking, if you apply mt.exe to everything in your \perl\bin directory, along with all the dlls that are in perl\lib\auto\*\*.dll and perl\site\lib\auto\*\*.dll; and if running the script passes the validation prior to being packaged, it should also pass validation after it's be packaged and unpacked.

Again, that purely a thoughware suggestion.