Add example of initialization of Hash.push

lib/Type/Hash.pod

@@ -127,4 +127,16 @@ Example:
     %h.push: a => [ 1 xx 3 ];           # a => [1,1,1,1,1]
     %h.push: b => 3;                    # a => [1,1,1,1,1], b => 3
 
+Also note that push can be used as a replacement for assignment during hash
+initialization very useful ways. Take for instance the case of an inverted
+index:
+
+    my %wc = 'hash' => 323, 'pair' => 322, 'pipe' => 323;
+    (my %inv).push: %wc.invert.unique;
+    say %inv;                           # 322 => 'pair', 323 => ['hash','pipe']
+
+Note that such a initialization could also be written as
+
+    my %inv .= push: %wc.invert.unique;
+
 =end pod