This can be found in the node mentioned above, the Perl Cookbook and a few other places.

@array1 = (1,2,3,4,5);
@array2 = (2,4,6,8,10);

%map2 = map {$_ => 1} @array2;

@intersection = grep ($map2{$_}, @array1);

print "@intersection\n";
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--
Steve Marvell