#!/usr/bin/perl

# -----

@mylist = ("gamma", "beta", "alpha", "alf");
@sortedlist = sort @mylist;
print "@sortedlist\n";

# -----

sub by_number {
  # Perl knows that $a and $b are the items to be compared
  if ($a < $b) {
    -1
  }
  elsif ($a > $b) {
    1
  }
  else {
    0
  }
}

@numbers = (3, 6, 18, 12, 2, 4, -3);

@sortedlist = sort by_number @numbers;
print "@sortedlist\n";

# -----

sub reverse_order { $b <=> $a }

@sortedlist = sort reverse_order @numbers;
print "@sortedlist\n";

# -----

# This is the default:
sub alphabetically { $a cmp $b }

sub case_insensitive { "\L$a" cmp "\L$b" }

@string_list = ("a", "john", "Mary", "kyle", "Kim", "polly", "B", "brenda");

@alpha_list = sort alphabetically @string_list;
@case_list = sort case_insensitive @string_list;
print "@alpha_list\n";
print "@case_list\n";

# -----

sub by_value { $hash_table{$b} <=> $hash_table{$a} }

%hash_table = ("benny" => 5, "bjorn" => 6,
                  "agnetha" => 9, "anifrid" => 4);

@ordered_list = sort by_value keys %hash_table;
print "@ordered_list\n";

# -----

sub by_value_and_key { 
  $hash_table{$b} <=> $hash_table{$a}  # descending order
    or
  $a cmp $b  # alphabetically
}

%hash_table = ("benny" => 6, "bjorn" => 6,
                  "agnetha" => 9, "anifrid" => 4);
@ordered_list = sort by_value_and_key keys %hash_table;
print "@ordered_list\n";

# -----