use strict;
use warnings;

my %hash = map { $_ => 1 } qw( foo food dood );

my @svalues1 = @hash{ sort { $a=~tr/d// <=> $b=~tr/d// } keys %hash };
my @svalues2 = @hash{ sort { $a=~tr/d// <=> $b=~tr/d// } %hash };

print(0+@svalues1, "\n");  # 3
print(0+@svalues2, "\n");  # 6