Basically, you want to build a hash keyed off of IPaddress+Action, whose value is the data-line of the file.

Let us call the hash

    my %ip_address;
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As you read your data file, you check to see if you have seen this action for this IP. If you have, then drop the data and go on to the next; if you haven't, then added the key/value to %ip_address.

Once you have read to the end of the data, your hash will contain the first occurances of each IPaddress+action. This pseudo-code (note: it only looks vaguely like Perl, not tested) shows you how to extract and sort to get the final report:

foreach my $data_line ( sort values %ip_action ) {
    print($data_line);
}
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