packaged for wip by mef.
List::Pairwise provides functions to map and grep lists two
elements at a time, setting $a and $b to each pair instead of
setting $_ to each element.
As of version 1.01, List::Pairwise now tries to use the newly
implemented XS functions pairmap, pairgrep, pairfirst and
pairs from List::Util 1.31 and up, resulting in a major
speedup.
New code should now preferably use List::Util functions
directly, with the added benefit of relying on a Perl core
module.
