/^(?=.*a)(?=.*b)(?=.*c).*d/
   or die;

##</code><code>##

my %order;
@order{qw( a b c d )} =
      map length, /^(?=(.*?)a)(?=(.*?)b)(?=(.*?)c)(.*?)d/
   or die;

my @ordered = sort { $order{$a} <=> $order{$b} } keys %order;

##</code><code>##

my @order = map length, /^(?=(.*?)a)(?=(.*?)b)(?=(.*?)c)(.*?)d/
   or die;

my @ordered = ( qw( a b c d ) )[
   sort { $order[$a] <=> $order[$b] } 0..$#order
];

##</code><code>##

my @unordered = qw( a b c d );

my @order;
for my $s (@unordered) {
   push @order, /\Q$s/ ? $-[0] : die;
}

my @ordered = @unordered[
   sort { $order[$a] <=> $order[$b] } 0..$#order
];