subprograms.fs

program foo
	123 constant qwe
	variable x  variable y
	: part-one blah qwe something x ! ;
	: part-two blah blah something-else y !;
	: part-three blah blah x @ y @ * or whatever ;
	main: part-one part-two part-three ;
end-program

program bar
	variable x  ( different from foo's x )
	: part-one x @ dup 1+ x ! ;  ( different from foo's part-one )
	( when bar recurses, the inner bar gets its own instance of x, like
	stack frames in c )
	main: part-one 1 and if bar then ;
end-program

( call foo and bar as words themselves, and they execute with their own private
contexts per each invokation )
: baz foo bar ;