I can't believe this worked.

returnvalues.pl

#!/usr/bin/perl
use v5.10;
use IO::File qw//;
sub countItems {
    (my $target) = @_;
    my $fh = IO::File->new('.ptd', 'r') or die 'no .ptd file found';
    return map { /^$target:(.*)/ } <$fh>;
}

sub printTodo {
    my @todo = countItems('todo'); my @done = countItems('done');
    my $t = 1; my $d = 1;
    say 'todo:';
    for my $todo (@todo) { print "$t:$todo"; $t++; }
    say 'done:';
    for my $done (@done) { print "$d:$done"; $d++; }
    exit;
}