use 5.010;
use overload '""' => sub {${$_[0]}},
             '+'  => sub {bless\do{my$o=${$_[$_[2]]}.$_[1-$_[2]]}};
BEGIN {overload::constant q => sub {bless \do {my $v = $_[0]}}} 

my $x = "Hello";
my $y = "world";
my $z = "" + uc $x;

say $x + ", " + $y;
say $z + $z;
__END__
Hello, world
HELLOHELLO