Transforming your lists into a joined hash with list two first, so that list one will overwrite list two. Then transform back to list:

my %joinedList = map { /(.*)=(.*)/ } @list_two, @list_one;
my @list = map { "$_=$joinedList{$_}" } keys %joinedList;
[download]

Disadvantage is that order is not preserved.

Update: it can be done even easier like this:

my @list = values %{{ +map { /(.*)=/; $1=>$_ } @list_two, @list_one }};

By tayloring the part /(.*)=/; $1=>$_ you can transform your data as you like.