The big win with the second is not that it is shorter to write, it is that it executes more efficiently because you do not have to recopy the existing string. Try this:

my $t = '';
$t .= "test" for 1..50_000;
[download]

versus

my $t = '';
$t = $t . "test" for 1..50_000;
[download]

See what I mean?