Rephrases routine def

Explanation in the #perl6 channel log http://colabti.org/irclogger/irclogger_log/perl6?date=2018-07-11#l182

Author: JJ

doc/Language/functions.pod6

@@ -4,10 +4,11 @@
 
 =SUBTITLE Functions and functional programming in Perl 6
 
-Routines are the smallest means of code reuse in Perl 6. They come in several
-forms, most notably L<methods|/type/Method>, which belong in classes and roles
-and are associated with an object; and functions (also called I<subroutines> or
-L<sub|/type/Sub>s, for short), which can be called independently of objects.
+Routines are one of the means Perl 6 has to reuse code. They come in
+several forms, most notably L<methods|/type/Method>, which belong in
+classes and roles and are associated with an object; and functions (also
+called I<subroutines> or L<sub|/type/Sub>s, for short), which can be
+called independently of objects.
 
 Subroutines default to lexical (C<my>) scoping, and calls to them are
 generally resolved at compile time.