use print_code for CODE_EXECUTE_HOOK
define 'case' syntax in (pircin core-syntax) library
export core syntaces from (scheme base)
define macro primitives (such as make-syntactic-closure) in (picrin macro)
[bugfix] identifier=? dies when take auxiliary syntax (because they emit
errors during expansion)
rewrite core syntaces with explicit renaming macro
[bugfix] let may take an identifier as a loop name
ir-macro-transformer seems not work properly
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