What moritz said. This would be a start, which you might need to tweak based on any unmentioned requirements:

use Regexp::Common qw(net);

while (<>) {
    my ($keeper) = $_ =~ /
        ($RE{net}{IPv4})    # Capture the IP
        ,                   # comma
        /x;
    printf "%s\n", $keeper if $keeper;
}
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