Error has been reported already and fixed in R2/Forward, but it hasn't made it into R2 yet

map-each

map-each: func [
	"Evaluates a block for each value(s) in a series and returns them as a block."
	[throw catch]
	'word [word! block!] "Word or block of words to set each time (local)"
	data [block!] "The series to traverse"
	body [block!] "Block to evaluate each time"
	/into "Collect into a given series, rather than a new block"
	output [any-block! any-string!] "The series to output to" ; Not image!
	/local init len x
][
	; Shortcut return for empty data
	either empty? data [any [output make block! 0]] [
		; BIND/copy word and body
		word: either block? word [
			if empty? word [throw make error! [script invalid-arg []]]
			copy/deep word  ; /deep because word is rebound before errors checked
		] [reduce [word]]
		word: use word reduce [word]
		body: bind/copy body first word
		; Build init code
		init: none
		parse word [any [word! | x: set-word! (
			unless init [init: make block! 4]
			; Add [x: at data index] to init, and remove from word
			insert insert insert tail init first x [at data] index? x
			remove x
		) :x | x: skip (
			throw make error! reduce ['script 'expect-set [word! set-word!] type? first x]
		)]]
		len: length? word ; Can be zero now (for advanced code tricks)
		; Create the output series if not specified
		unless into [output: make block! divide length? data max 1 len]
		; Process the data (which is not empty at this point)
		until [ ; Note: output: insert/only output needed for list! output
			set word data  do init
			unless unset? set/any 'x do body [output: insert/only output :x]
			tail? data: skip data len
		]
		; Return the output and clean up memory references
		also either into [output] [head output] (
			set [word data body output init x] none
		)
	]
]