Sometimes the Perl sugar is pretty sweet, though.

  my %h1 = ("xyz" => 2);
  my %h2 = ("abc" => 9, "def" => 3);
  # hashmap from Hash::MostUtils
  my %hash = hashmap { "$b-$a" => $a * $b } 
             %h1, %h2, "eieio" => 0, "abc" => 1;

  # "0-eieio" => "",
  # "1-abc" -> "abc"
  # "2-xyz" => "xyzxyz"
  # "3-def" => "defdefdef"