This works on my system, (linux, so you'll need to tweak the locations of things), though it's a bit of a kludge.

#!/usr/bin/perl -w

open NAMES, "names.txt" or die "Cannot open names file";

while (<NAMES>) {
    chomp;
    my $ping = `ping -c 1 $_`;

    if ($ping =~ /\((\d+\.\d+\.\d+\.\d+)\)/) {
    my $ip = $1;
    open TESTED, '>>tested.txt';
    print TESTED "$ip\n";
    close TESTED;
    } else {
    warn "Cannot deciper result of \"ping $_\"";
    }
}

close NAMES;
exit 0;
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Originally posted as a Categorized Answer.