{"body":"class ImmutableDS {\n   has $!last-return;\n   has $.field-value;\n   has $.some-field is rw = Proxy.new:\n      FETCH => method { my $tmp = $!last-return; $!last-return := Nil; $tmp // $!field-value },\n      STORE => method ($field-value) { $!last-return = self.clone: :$field-value }\n   ;\n}\n\n\nmy ImmutableDS $immutable-data-structure .= new: :42field-value;\nmy $new-immutable-data-structure = $immutable-data-structure.some-field = 13;\nsay $new-immutable-data-structure.some-field;\nsay $immutable-data-structure.some-field;","name":"","extension":"txt","url":"https://www.irccloud.com/pastebin/sHSXlm2x","modified":1591177475,"id":"sHSXlm2x","size":521,"lines":14,"own_paste":false,"theme":"","date":1591177475}