Perl module Privileges::Drop Portfile Fails to Build on Azure

[Steven Smith]

I have a simple perl module Privileges::Drop Portfile as part of PR https://github.com/macports/macports-ports/pull/5482 that builds fine on multiple boxes locally, but fails on azure. The error is:

https://paste.z0k.xyz/0b334360ab7f
Use of uninitialized value $_[0] in substitution (s///) at /opt/local/lib/perl5/5.26/File/Basename.pm line 341.
fileparse(): need a valid pathname at /opt/local/lib/perl5/5.26/CPAN/FirstTime.pm line 1413.
Command failed:  cd "/opt/local/var/macports/build/_Users_vsts_agent_2.158.0_work_1_s_perl_p5-privileges-drop/p5.26-privileges-drop/work/Privileges-Drop-1.03" && /opt/local/bin/perl5.26 Makefile.PL INSTALLDIRS=vendor CC="/usr/bin/clang" LD="/usr/bin/clang" 
Exit code: 255

I’m at a loss to see the cause or fix. Any pointers would be appreciated.
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