My biggest concern is your statement that the commands "do not execute". What sort of diagnostics are you using? I notice you're not checking the return from $ssh->cmd at all. Try something like:
($out, $error, $exit) = $ssh->cmd("...");
What happens if you SSH to the machine in question like so (assuming your script also runs on a Unix/Linux platform):
ssh firstname.lastname@example.org show lb vserver (lbserver_value)
It may be that your "show" command is not in a standard $PATH location on the target system. It may work when you log in, if your shell startup scripts (.bashrc and the like) append to $PATH, but may not work when you do not have a login shell. You can also try specifying the full path to "show".