I came up with this, at 46 chars:

@array=do{grep$_{$_}<2,grep{!$_{$_}++}@array};
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Of course, if we were truely golfing, that comes out at:

sub find_duplicates {

#23456789_123456789_123456789_
grep$_{$_}<2,grep{!$_{$_}++}@_

}
[download]

30 characters :)