Perl5.28 not using $PERL5LIB to populate @INC

[hyperbole (hyperbole)]

I just used MacPorts to install perl5.28 on my MacBookPro running High Sierra (v-10.13.6). When I run perl from the terminal window in debug mode, and print @INC, I see the following:

DB<1> x @INC

0 '/Users/carlreynolds/modules'

1 '/opt/local/lib/perl5/5.28/darwin-thread-multi-2level'

2 '/opt/local/lib/perl5/5.28'

3 '/opt/local/lib/perl5/5.28/darwin-thread-multi-2level'

4 '/opt/local/lib/perl5/site_perl/5.28/darwin-thread-multi-2level'

5 '/opt/local/lib/perl5/site_perl/5.28'

6 '/opt/local/lib/perl5/vendor_perl/5.28/darwin-thread-multi-2level'

7 '/opt/local/lib/perl5/vendor_perl/5.28'

8 '/opt/local/lib/perl5/5.28/darwin-thread-multi-2level'

9 '/opt/local/lib/perl5/5.28'

However,

DB<2> x $ENV{'PERLLIB'}, $ENV{'PERL5LIB'}

0 '/Users/carlreynolds/modules:/opt/local/lib/perl5/5.28:/opt/local/lib/perl5/5.28/darwin-thread-multi-2level'

1 '/Users/carlreynolds/modules:/opt/local/lib/perl5/5.28:/opt/local/lib/perl5/5.28/darwin-thread-multi-2level'

Do you know why this version of perl is not using my definition of $PERL5LIB to set @INC? It looks to me as if @INC was compiled into perl when MacPorts installed it.

Thanks for any help you can give me,

Carl.