use strict;
use warnings;

# Set up hash with prominent marker key/value pairs
# and a load of fillers. No 'Foo' yet.
#
my %hash = (
   Bib => 387,
   Bob => 745,
   Baz  => 106);
$hash{$_} = int rand 10
   for q{Bea} .. q{Bep};

my @keysOrder = ();
my @prefOrder = ();
my $key;

# Push key and value strings onto array in keys order.
#
foreach $key (keys %hash)
{
    push @keysOrder, qq{$key => $hash{$key}};
}

# Push key and value strings onto another array in
# preferred order.
#
foreach my $key (prefOrder(keys %hash))
{
    push @prefOrder, qq{$key => $hash{$key}};
}

# Print results side by side for comparison.
#
print qq{\nKey Order     Preferred Order\n};
for (0 .. $#keysOrder)
{
    printf qq{%-14s%-14s\n}, $keysOrder[$_], $prefOrder[$_];
}

# Add 'Foo' to the hash and repeat test.
#
$hash{Foo} = 999;
@keysOrder = ();
@prefOrder = ();

foreach $key (keys %hash)
{
    push @keysOrder, qq{$key => $hash{$key}};
}

foreach my $key (prefOrder(keys %hash))
{
    push @prefOrder, qq{$key => $hash{$key}};
}

print qq{\nKey Order     Preferred Order\n};
for (0 .. $#keysOrder)
{
    printf qq{%-14s%-14s\n}, $keysOrder[$_], $prefOrder[$_];
}

sub prefOrder
{
    return
       map  {$_->[0]}
       sort {$b->[1] <=> $a->[1]}
       map  {[$_, $_ eq q{Foo}]}
       @_;
}