Add GLR lemma

Author: lizmat

S99-glossary.pod

@@ -684,6 +684,12 @@ keyword for the Perl 6 switch L</statement>.
 
 A L</pseudo-scope> for L</interpreter>-wide L</package> L</symbols>, really UNIT::GLOBAL.
 
+=head2 GLR
+
+The Great List Refactor: a refactoring of the reification of lazy lists, so that
+lazy evaluation is only done when it is really needed.  Expected to provide a
+performance benefit of several factors in certain, loop-like situations.
+
 =head2 golf
 
 Shortest possible way (least amount of typed characters) to get a program to do