[basics] add some verbage on scopes and sigils

src/basics.pod

@@ -90,22 +90,23 @@ X<lexical>
 X<variables, lexical>
 X<block>
 
-C<my> declares a lexical variable.  Lexical variables are visible only in
-the current block.  If there's no enclosing block, it's visible throughout the
-remainder of the file. A block is any part of the code enclosed between curly 
-braces { }.
+C<my> declares a lexical variable. Lexical variables are visible only
+in the current block from the point of declaration to the end of the
+block. If there's no enclosing block, it's visible throughout the
+remainder of the file. A block is any part of the code enclosed between
+curly braces { }.
 
 X<sigil>
 X<identifier>
 
-A variable name begins with a I<sigil>, which is non-alpha-numeric symbol
-such as
-C<$>, C<@>, C<%>, or C<&>--or occasionally the double colon C<::>. The sigils
-usually restrict the variable to a particular type, such as a single value or a
-compound value.  After the sigil comes an I<identifier>, which may consist of
-letters, digits and the underscore. Between letters you can also use a dash
-C<-> or an apostrophe C<'>, so C<isn't> and C<double-click> are valid
-identifiers.
+A variable name begins with a I<sigil>, which is non-alpha-numeric
+symbol such as C<$>, C<@>, C<%>, or C<&>--or occasionally the double
+colon C<::>. Sigils indicate the structural interface for the variable,
+such as whether it should be treated as a single value or a compound value
+or a subroutine, etc. After the sigil comes an I<identifier>, which may
+consist of letters, digits and the underscore. Between letters you can
+also use a dash C<-> or an apostrophe C<'>, so C<isn't> and C<double-
+click> are valid identifiers.
 
 X<variable, scalar>
 X<scalar>
@@ -182,6 +183,13 @@ C<[ ]> or C<{ }>. This is called I<M<sigil invariance>>.>.
 In the score counting program, C<%matches> stores the number of matches each
 player has won.  C<%sets> stores the number of sets each player has won.
 
+
+=for author
+
+The following paragraph seems out of place.
+
+=end
+
 Sigils indicate the default access method for a variable. Variables
 with the C<@> sigil are accessed positionally; variables with the C<%>
 sigil are accessed by string key. The C<$> sigil, however, indicates a