Hashes

 
  %longday = ( "Sun" => "Sunday",
               "Mon" => "Monday");           
  %map = ();                      # clear hash 
  %params =  @ARGV;               # copy an array to a hash
  $map{ Sun} = "Sunday";
  print $longday{"Sun"};
  foreach $var (sort keys %ENV)
  {
    print "$var: " . $ENV{ $var} . "\n";
  }
#
# Hash references
#
 $rh = { "laurel" => "hardy", 
         "romeo" => "juliet"}; # reference to an anon hash
 $$rh{"key") = "VAL";   
 $rh->{"key") = "VAL";
 foreach my $key (sort keys %$rh){...}
#
# Temporary anonymous hash
#
foreach my $key ( keys %{$h = {qw( start 0 stop 100)}})
{
    print " $key -> $h->{ $key}\n";
}