Cannot load config file: couldn't open /Users/me/perl/perl_lib:/usr/local/lib/perl5/site_perl/

That's not a problem with the setting of $PERL5LIB, that's a problem with how your perl script is using it. Since you haven't shown your script I can't help you further with that.

BTW, there is no effect in exporting the same variable twice in sh/bash.

Update: just for completeness, here's a demo showing multiple entries in $PERL5LIB.

use strict;
use warnings;

use Path::Tiny;
use Test::More tests => 3;

chdir '/'; # In case you have . in @INC
my $mod = path ('/tmp')->child ('ZZZZZ.pm');
$mod->spew ('package ZZZZZ;1;');
ok ! system ("PERL5LIB=/tmp:/foo perl -e 'use ZZZZZ;'"), 'First in pat
+h';
ok ! system ("PERL5LIB=/foo:/tmp perl -e 'use ZZZZZ;'"), 'Second in pa
+th';
ok   system ("PERL5LIB=/foo:/bar perl -e 'use ZZZZZ;'"), 'Not in path'
+;
$mod->remove;
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