eval

(eval datum env) evaluates a datum at run time, on every backend. Every environment specifier is the one global environment: (interaction-environment), (scheme-report-environment 5), (environment '(scheme base) ...) -- its import sets are checked against the libraries -- and MIT Scheme's user-initial-environment and system-global-environment all name it, and the argument may be left out (not under --scheme-standard r7rs). It holds the program's variables (including what eval itself defined), the program's procedures, and the built-in procedures, in that order. A define inside eval is a program global, visible to later evals and to the program itself (through eval -- a name first defined this way has no compiled direct reference), and a set! of one of the program's variables assigns it: the program reads what eval wrote.

#t
(3628800 10000)

Inside eval, a named let, a do and a procedure calling itself run in constant stack; every other call uses it. define-record-type, define-values, let-values, and import are refused by name inside eval. A compiled program's eval resolves a built-in procedure only when the program spells its name somewhere -- as a symbol, quoted data included, or inside a string -- while the interpreter resolves them all.