Since you open ping.txt for reading and immediately for writing, you globber the file. That's why is empty (apart from the statistics lines you put in).
because of that, @results will be an empty list, which saves you from the next problem: the infinite loop in while (@results) {...}

To loop over all elements of result, use:

foreach (@results) { ... }
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Use different files for reading and writing or read the file first, then reopen it for writing.

Lastly, put

use strict;
use warnings;
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on top off your programs :)