Thank you for your suggestions, but let me clarify a couple of points:

1. The problem isn’t PERL5LIB, but environment variables.   (EPIC does have a well-defined and workable way to specify the Perl include-path .. @INC ... to use for a particular project.)
2. The behavior that is adversely affected by the lack of environment variables is simply the built-in syntax checking (red “X” in the margin to the left of a line, indicating an error was found there).
3. You can set the environment-variables that are associated with a GUI icon in OS/X, as detailed in the Apple technical article (third bullet point in the OP).

What I would “like to have” is the ability to specify environment variable settings, as well as the @INC path, on a per-project basis.   However, in any case, the impact to me is negligible, and the code in question is definitely “the odd man out.”