Document that empty PATH components are also insecure.

[dakkar]

I was recently surprised by a change in behaviour between perl 5.36 and 5.38: an empty $ENV{PATH} triggered the "Insecure directory" error under taint mode.

That is correct and desired behaviour (see 5ede445 (and technically 9eb153f and 92ec2fc)), but the documentation makes no mention of this.

Now it does.

---

• This set of changes does not require a perldelta entry.

[demerphq]

Note there is a test failure:

porting/bincompat.t ....... ok

#   Failed test 'Is mailmap_file '.mailmap' up to date?'
#   at Porting/updateAUTHORS.pl line [12](https://github.com/Perl/perl5/actions/runs/11052824202/job/30705762942?pr=22625#step:12:13)6.
#   File '.mailmap' changes:
#     would add: Gianni Ceccarelli <[email protected]> dakkar <[email protected]>
# 
# Files need updating! You probably just need to run
# 
#    Porting/updateAUTHORS.pl
# 
# and commit the results.

So you need to tweak this before we can merge it. Thanks for the patch BTW, I overlooked the need to update these docs.