Removing references to "interpolation"

Slightly rewording and explaining what a twigil is, too. Following @treyharris pointed advice on the thoughts on the original test. Closes #2588

Author: JJ

doc/Language/variables.pod6

@@ -219,10 +219,10 @@ See L<Binding|/language/containers#Binding> for more information.
 =head1 Twigils
 X<|Twigil>
 
-Twigils influence the scoping of a variable; however, they
-have no influence over whether the primary sigil interpolates. That is, if
-C<$a> interpolates, so do C<$^a>, C<$*a>, C<$=a>, C<$?a>, C<$.a>, etc.  It
-only depends on the C<$>.
+We use the term twigils, a word play with I<sigil>, that indicates it uses two
+symbols in front of an identifier; the second symbol will be placed between
+the sigil and the identifier, and it will be related to the scoping of a
+variable, that is, where that variable is defined and can be changed.
 
 =begin table