## your code is effectively this:
   my %hash_list = ( " Bill 34", " Jane 28", " John 20", " Tom 19", " Wall 18" );

   ## which means...
   my %hash_list = (
      # key         # value
      " Bill 34" => " Jane 28",
      " John 20" => " Tom 19",
      " Wall 18  => undef
   );