Revision history for Spp

0.01    2015-11-1
        First version, released on an unsuspecting world.

0.02    2015-11-2
        to-rule use JSON function encode_json.

0.03    2015-12-2
        repl spp is interface of spp

0.04    2017-08-14
        Spp as Parser of grammar, not entire language like lisp

1.01    2017-08-18
        Spp could use as app to test

1.02    2017-8-21
        fix bug could not install. readme add some content.

1.03    2017-8-29
        fix some bug, add string and str to Str

1.04    2017-8-29
        rewrite repl and Spp.pm

1.05    2017-8-29
        delete two no use function, is_str_atom() rename is_str()