$h->{first_name} = $h->{name};
delete $h->{name};

##</code><code>##

my $h = {
    mm        => 'July',
    yyyy      => '1975',
    dd        => '31',
    name      => 'Milo',
    last_name => 'Manara',
};

my %replacement_for = ( mm   => 'month',
                        yyyy => 'year',
                        dd   => 'day',
                        name => 'first_name', );

my @array_from_hash = %$h;
my $x = 0;
for ( @array_from_hash ) {
    if ( $x++ % 2 == 0 && exists $replacement_for{$_} ) {
        $_ = $replacement_for{$_};
    }
}

my $h2 = { @array_from_hash };

print Dumper $h;
print Dumper $h2;
__END__
$VAR1 = { 
          'mm' => 'July',
          'name' => 'Milo',
          'dd' => '31',
          'last_name' => 'Manara',
          'yyyy' => '1975'
        };
$VAR1 = { 
          'month' => 'July',
          'day' => '31',
          'year' => '1975',
          'last_name' => 'Manara',
          'first_name' => 'Milo'
        };