How to concatenate strings with Perl?

Method #1 - using Perl's dot operator:
$name = 'checkbook';
$filename = "/tmp/" . $name . ".tmp";

Method #2 - using Perl's join function
$name = "checkbook";
$filename = join "", "/tmp/", $name, ".tmp";

Method #3 - usual way of concatenating strings
$filename = "/tmp/${name}.tmp";