?: is the ternary operator.

it's equivalent to 

 
push @{ 
    if( $count{$element} > 1 )
    {
        \@intersection;
    }
    else
    {
        \@difference;
    }
}, $element;

[download]
(though a little less verbose)

~Particle *accelerates*

In reply to Re: union, intersection, and difference by particle
in thread union, intersection, and difference by trowa

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