OK, can the left side of the = still be any expression? Since I won't know what the results are until after I get them and they'll be different for each device, I don't see how I can hard code them to a var.

No. For example, the following will fail:

print("Hello World") = 3;
[download]

for my $ip (...) {
   my $res = ...;
   my ($image) = ...;
   print("$ip: $image\n");
}
[download]