Just like in perlfaq4, except the uniqueness constraint is join('|', @{$_}[0..2]) instead of $_. 

my %seen;
@array = grep !$seen{ join('|', @{$_}[0..2]) }++, @array;

[download]

Update: Added missing comma.

In reply to Re: How to Eliminate duplicate entry by ikegami
in thread How to Eliminate duplicate entry by Anonymous Monk

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