I am bringing this up because I use dmenu and when it tries to build a cache, it throws up this path error.

Something totally unrelated is that manpages give strange error messages due to the non-existing directories in $PATH.
See http://bbs.archlinux.org/viewtopic.php?id=76528
This is something totally possible to fix before deciding on 13808, you could just comment & replace the entry temporarily in perlbin.sh before making the pkg...

Edit:
Independently to http://bugs.archlinux.org/task/13808 -- write this into the perlbin.sh:

for add in /usr/bin/perlbin/core /usr/bin/perlbin/site /usr/bin/perlbin/vendor; do
[[ -d $add ]] && PATH="$PATH:$add"
done

While this isn't really an error in UNIX I'll implement this in 5.12.0.