while is not setting $_ for you. in

while (<PINGALLIP>) {
   if (/is alive/) {
      chomp;
      print ALIVEIP $_;
   }
}
[download]

Try this instead:

/is alive/ and print ALIVEIP for <PINGALLIP>;
[download]

If the match is true then print $_ for all lines. I omitted chomp since the record delimiters will probably be handy in the file.

After Compline,
Zaxo