use strict;
use warnings;

my %hash = ( 
    one   => 1, 
    two   => 2, 
    three => 3, 
    four  => 4, 
    five  => 5 
);

my $priority_key = 'three';

sub prioritize {
    my( $href, $find ) = @_;
    my @prioritized_keys;
    while( my( $key, $value ) = each %{$href} ) {
        if( $key ne $find ) {
            push @prioritized_keys, $key;
        } else {
            unshift @prioritized_keys, $key;
        }
    }
    return \@prioritized_keys;
}

my @keyset = @{ prioritize( \%hash, $priority_key ) };

print "@keyset\n";

##</code><code>##

use strict;
use warnings;

my %hash = ( 
    one   => 1, 
    two   => 2, 
    three => 3, 
    four  => 4, 
    five  => 5 
);

my $priority_key = 'three';

sub prioritize {
    my( $href, $find ) = @_;
    my @keyring = keys %{$href};
    foreach my $idx ( 0 .. $#keyring ) {
        next unless $keyring[ $idx ] eq $find;
        unshift( @keyring, splice( @keyring, $idx, 1 ) );
        last;
    }
    return \@keyring;
}

my @keyset = @{ prioritize( \%hash, $priority_key ) };

print "@keyset\n";