# chickadee » begin-syntax » begin-syntax

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(begin-syntax EXPR ...)syntax

Evaluates its body and immediately inserts the final result into the program, as though by macro expansion.

If the result is a macro transformer, then this is immediately invoked with no arguments and the result is inserted into the program. Note that in this case the final expression of the begin-syntax body will be evaluated twice.

This form can be thought of as a macro definition followed by its immediate expansion, for example:

```(begin-syntax '(+ 1 2))

; => (let-syntax ((a (er-macro-transformer
;                     (lambda (_ _ _) '(+ 1 2)))))
;      (a))```