I can't believe this worked.

returnvalues.pl

sub countItems {
    (my $target) = @_;
    open(TODO, "./.ptd") or die "please create a .ptd file";
    @_ = ();
    for $_ (<TODO>) { push @_, $1 if /^$target:(.*)$/; }

    return @_;
}

sub printTodo {
    my @todo = countItems("todo"); my @done = countItems("done");
    my $t = 1; my $d = 1;
    print "todo:\n";
    for my $todo (@todo) { print "$t:$todo\n"; $t++; }
    print "done:\n";
    for my $done (@done) { print "$d:$done\n"; $d++; }
    exit;
}