I have never seen anybody even come close to isolating what causes some installs to exhibit this problem while other installs do not.

Now you have! :)

But only as a result of your prompting my memory with your post:

C:\test>set PATHEXT=.COM;.EXE;.BAT;.CMD;

C:\test>junk.pl junk.pl
'print "'$_'" while <>;
'
C:\test>junk junk.pl

C:\test>set PATHEXT=.pl;.COM;.EXE;.BAT;.CMD;

C:\test>junk junk.pl
'print "'$_'" while <>;
'
[download]

Personally, I dislike pl2bat with a vengeance. I've tried it several time over the years and always abandoned it almost immediately for one reason or another. I haven't tried to use it now for several years and can't remember all of the reasons.

But the Terminate batch job (Y/N)? prompting is only one.

Another is it screws up syntax highlighting. I could associate .bat with the .pl profile, but then that screws up highlighting in .bats. Another is forgetting that I pl2bat'd some script and the spending a few minutes--or on one particularly memorable occasion a few days--tearing my hair out before working out why none of the changes I was making to the .pl file were affecting the output from the script :)

Dumb! But I've done it several times. There are others. Perl::Tidy etc. Yes. It is just a matter of discipline. And only pl2batting once you've finished developing which is reasonably easy to do. But it's when you come back to something a few months or years later that it goes tits up.

Once you have PATHEXT/ASSOC/FTYPE set up correctly, everything "Just works". And setting it up is a one-time deal. I also like the multiple side-by-side perl installs that it affords through the simple mechanism of using different extensions .pl for 5.latest, .pl8 for 5.8 etc.