From: <clingmans-dome.ascent.com at pao> (Patrick A. O'Donnell)
   
       Replacing MAPCAR with MAPC is equivalent, but requires less change to
       your source.
   
   	...  using closures can be cons-intensive ...
   
       Starting in 4.3 closures are stack consed ...
   
   I'd also like to note that both of these operations would be most
   likely to generate short-lived objects, which the global gc would
   never see.  Since my problem is with the global gc (scavenges seem
   quick enough in general), these will not be likely to help.
   
This isn't quite an accurate analysis.  Remember that ephemeral
consing drives newspace scavenging, and objects surviving some number
(typically 5) scavenges are tenured.  Accumulation of tenured objects
drives global gc.

Therefore, unnecessary ephemeral consing increases the liklihood that
other intermediate-lived objects will become tenured and thus
increases the frequency of global gc.