my $cnt = keys %{$self->{is_tested}};
        my $newenv = join $Config::Config{path_sep}, @dirs, @env;
        $CPAN::Frontend->optprint('perl5lib', sprintf ("Prepending blib/arch and blib/lib of ".
                                 "%d build dirs to PERL5LIB, reaching size %d; ".
                                 "for '%s'\n", $cnt, length($newenv), $for)
                                );
        $ENV{PERL5LIB} = $newenv;