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  return preserve_context { some::code() }
             after => sub { $_ += 42 for @_ };

=head1 DESCRIPTION

Sometimes you need to call a function, get the results, act on the
results, then return the result of the function.  This is painful
because of contexts; the original function can behave different if
it's called in void, scalar, or list context.  You can ignore the
various cases and just pick one, but that's fragile.  To do things
right, you need to see which case you're being called in, and then
call the function in that context.  This results in 3 code paths,
which is a pain to type in (and maintain).

This module automates the process.  You provide a coderef that is the
"original function", and another coderef to run after the original
runs.  You can modify the return value (aliased to @_) here, and do
whatever else you need to do.  C<wantarray> is correct inside both
coderefs; in "after", though, the return value is ignored and the
value C<wantarray> returns is related to the context that the original