my $password = $ARGV[0]; has been working fine in my password-sensitive scripts for ages.

The smiley appears to be missing from the end of that line :-)

For those who are thinking of following this advice, be aware that having your script accept the password as a command line argument means that the plaintext password will be visible to anyone looking over your shoulder, anyone who can run the ps command, anyone who can read your shell's command history file etc, etc, etc.