UNIX for Dummies Questions & Answers

#!/usr/bin/perl

use Socket;

# While sdtin
while(<>) {
	chomp($_);
	if($_ =~ /(\d+\.\d+\.\d+\.)(\d+)\s+(\d+)/) {
		for($2..$3) {
			$iaddr = inet_aton( "$1$_" );
			print "$1$_ = ".(gethostbyaddr($iaddr, AF_INET) or "hostname not found")."\n";
		}
	} elsif($_ =~ /(\d+\.\d+\.\d+\.\d+)/ ) { 
		$iaddr = inet_aton( $1 );
		print "$1 = ".(gethostbyaddr($iaddr, AF_INET) or "hostname not found")."\n";
	} else {
		print "Invalid ip\n";
	}
}