$pop = new Mail::POP3Client("user", "pwd"[, "host"[, port[, debug]]])
Constructor. Creates a new POP3 connection. The arguments are:
- user
 The username.
- pwd
 The password.
- host
 Optional. The POP3 host; defaults to pop.
- port
 Optional. The POP3 port number; defaults to 110.
- debug
 Enables debugging (to STDERR) on the object if set to a positive integer.
Defaults to 0.