Better change order of those lines:

if ($line =~ m/:.+\@.+\s([0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3
+})/)
{
  Xchat::print("test2",,$servertabname);
  my $ip = $1;
[download]

to

if ($line =~ m/:.+\@.+\s([0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3
+})/)
{
  my $ip = $1;
  Xchat::print("test2",,$servertabname);
[download]

If there is any regexp inside Xchat::print() method, it will reset $1. Maybe this is your case?

BTW. [0-9] can be written as \d