"...Who broke our code"

I'm not sure. Probably it was the author?

It might be easier to install perlbrew instead of rewriting your beloved toolchain:

karls-mac-mini:hook karl$ perl -MPOSIX=tmpnam -e 1
Unimplemented: POSIX::tmpnam(): use File::Temp instead at /Users/karl/
+perl5/perlbrew/perls/perl-5.26.2/lib/5.26.2/darwin-2level/POSIX.pm li
+ne 185.
Unimplemented: POSIX::tmpnam() at -e line 0.
BEGIN failed--compilation aborted.
karls-mac-mini:hook karl$ perlbrew list
  5.14.2threads
  perl-5.16.2
  perl-5.16.3
  perl-5.17.7
  perl-5.18.0
  perl-5.18.1
  perl-5.18.2
  perl-5.18.2threads
  perl-5.20.0
  perl-5.20.0threads
  perl-5.22.1-threads
  perl-5.24.1threads
* perl-5.26.2
karls-mac-mini:hook karl$ perlbrew use perl-5.24.1threads
karls-mac-mini:hook karl$ perl -MPOSIX=tmpnam -e 1
[download]

Yes, i know ... it's just a callow idea for the rescue in a hurry.

Best regards, Karl