You've got 2 of things to tweak

1. It's @ARGV so you want $ARGV[1]
2. I assume you want the first item from @ARGV which is $ARGV[0]

You also can just say $_ you don't need ${_}

But the best advice I can give you is, not to reinvent the wheel. Use nmap. Nmap does portscans and a heck of lot more. It can give a rough security profile of your system including a fingerprint if possible