Why doesn’t sudo -E preserve PERL5LIB on macOS?

I’m experiencing a strange behavior related to environment variable preservation with sudo on macOS(15.2): sudo -E doesn't preserve the environment variable PERL5LIB.

Reproduction Steps

1. Set an environment variable in the shell: export PERL5LIB=foo . The command env | grep PERL5LIB outputs as expected: PERL5LIB=foo .

2. However, the command sudo -E env | grep PERL5LIB , returns nothing. In contrast, this works: sudo --preserve-env=PERL5LIB env | grep PERL5LIB . It successfully preserves PERL5LIB.

This is confusing because I expected sudo -E to preserve all environment variables from the invoking shell, including PERL5LIB. But clearly, it’s not working that way for this particular variable.

Question

• Why is PERL5LIB not preserved by sudo -E on macOS?
• Is this behavior specific to PERL5LIB, or does it affect other variables as well?
• What is the recommended, reliable way to ensure that PERL5LIB is preserved when using sudo?

You can run :

$ sudo strings /usr/bin/sudo | grep PERL
PERLIO_DEBUG
PERLLIB
PERL5LIB
PERL5OPT
PERL5DB

They are considered potentially dangerous and removed by default.

I think the command you gave sudo --preserve-env=PERL5LIB env is the most secure, reliable way to ensure that PERL5LIB is preserved when using sudo.