Be more specific about RAKUDO_DEFAULT_READ_ELEMS

Author: stoned

doc/Programs/03-environment-variables.pod6

@@ -112,8 +112,9 @@ line editor; the default is C<~/.perl6/rakudo-history>.
 X<|RAKUDO_DEFAULT_READ_ELEMS>
 =item C<RAKUDO_DEFAULT_READ_ELEMS>
 
-Is the default number of characters to read on an C<IO::Handle>, defaults to
-65536 (aka 64K).
+This specifies the default number of characters to read on an L«C<IO::Handle>|/type/IO::Handle» by
+setting the L«C<$*DEFAULT-READ-ELEMS>|/language/variables#$*DEFAULT-READ-ELEMS»
+dynamic variable.
 
 X<|RAKUDO_ERROR_COLOR>
 =item C<RAKUDO_ERROR_COLOR>