Move :exists and :delete to new Data Structures section

lib/Language/5to6.pod

@@ -208,23 +208,6 @@ I<Key/value-slicing an array variable>
     say join ',', @months[6, 8..11]:kv; # Perl 6 - % becomes @; slice controlled by adverb
 =end item
 
-Some functions for manipulating hashes and querying hash values have been
-turned into adverbs:
-
-=begin item
-I<Checking for element existence in a hash>
-
-    say "element exists" if exists $hash{$key};  # Perl 5
-    say "element exists" if %hash{$key}:exists;  # Perl 6 - exists controlled by adverb
-=end item
-
-=begin item
-I<Deleting an element in a hash>
-
-    my $deleted_value = delete $hash{$key};  # Perl 5
-    my $deleted_value = %hash{$key}:delete;  # Perl 6 - delete controlled by adverb
-=end item
-
 =head4 C<&> Sub
 
 In Perl 6, the C<&> sigil is used consistently (and without the help of
@@ -575,8 +558,31 @@ translation.
 In scalar context, C<..> and C<...> were the little-known Flipflop
 operators. They have been replaced by C<ff> and C<fff>.
 
+=head2 Data Structures
+
+=head3 Arrays and Lists
 
+=head3 Hashes
 
+As mentioned above in the section on L<#Sigils>, hashes in Perl 6 are always
+prefixed with a C<%>.
+
+Some functions for manipulating hashes and querying hash values have been
+turned into adverbs:
+
+=begin item
+I<Checking for element existence in a hash>
+
+    say "element exists" if exists $hash{$key};  # Perl 5
+    say "element exists" if %hash{$key}:exists;  # Perl 6 - exists controlled by adverb
+=end item
+
+=begin item
+I<Deleting an element in a hash>
+
+    my $deleted_value = delete $hash{$key};  # Perl 5
+    my $deleted_value = %hash{$key}:delete;  # Perl 6 - delete controlled by adverb
+=end item
 
 =head2 Compound Statements