EXPORTED FUNCTION bisect my ($a,$b) = bisect {$_ <= 5} 1..10; # $a == [1..5] # $b == [6..10] Useage is like grep where you pass it a block and a list, returns a list of two arrayrefs. All TRUE values are put in to the first arrayref, FALSE in the second arrayref. trisect my ($a,$b,$c) = trisect {$_ <=> 5} 1..10; # $a == [1..4] # $b == [5] # $c == [6..10] Useage is like grep where you pass it a block and a list, returns a list of three arrayrefs. The intent here though is to break that list in to three parts using cmp-style returns (-1/0/1). All values that cause your codeblock to return -1 are in the first arrayref, 0 in the next, and everything else falls in the last arrayref. !!NOTE!! Currently the last arrayref is a catch all for anything that does not exactly match -1/0. If you write your own cusom block that returns any value other then -1/0/1 then it will end up here. This was done as I want to keep the expectation that all items from the input list will be found some where in the output. my ($x,$y,$z) = List::Bisect::trisect { $_ < 5 ? -1 : $_ > 5 ? 1 : 'foo' } 1..10; # $x == [1..4] # $y == [] # $z == [5..10]