Perl

#!/usr/bin/perl -wmy $ip_last_check_file = "/home/thomas/.currentip/ip";my $ip_now = `curl -s http://checkip.dyndns.org`;$ip_now =~ s/.*?(\d+\.\d+\.\d+\.\d+).*/$1/s;open(IP, "<$ip_last_check_file") or die "Cannot open $ip_last_check_file: $!";my $ip_last_check = <IP>;close(IP);if ($ip_now ne $ip_last_check){  open(IP, ">$ip_last_check_file") or die "Cannot open $ip_last_check: $!";  print IP $ip_now;  close(IP);}exit;