Assuming you want to retain a spanning set (which the golf seems to have gotten away from...)

@filtered = grep {!$seen{$_}++} @original;
#somewhat tested code
[download]

will give you one of each IP address in the list.

And it golfs pretty well, too...

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If God had meant us to fly, he would *never* have give us the railroads.
    --Michael Flanders