$ perl -E '
    use List::Util "first";
    use Tk;
    my $mw = MainWindow->new;
    my @font_prefs = ("Consolas", "Lucida Console", "Courier");
    my %font_have = map { fc $_ => 1 } $mw->fontFamilies;
    my $font_best = first { exists $font_have{fc $_} } @font_prefs;
    say $font_best
'
Courier