http://www.perlmonks.org?node_id=1045611


in reply to Re^3: Understanding the Schwartzian transform.
in thread Understanding the Schwartzian transform.

but, definitely, the "output_array = map {block} sort {block} map {block} input array" is the canonical for of the Schwartzian Transform.

Sorry, that is like the generic form of Guttman-Rosler Transforms (see links) except without the secret ingredient :)(normalize/restore)

Schwartzian is

my @sorted = map { restore_from_cache } sort { by_cached_expensive } map { store_cache_expensive } @original;