ARG \
	# multi-line arg
   ALPINE_VERSION=alpine:3.15.4

FROM \
${ALPINE_VERSION} as stage1

ARG   \
  \
 # multi-line arg
 # and multi-line comment
   nginx_version="nginx:1.18.0-alpine@sha256:ca9fac83c6c89a09424279de522214e865e322187b22a1a29b12747a4287b7bd"

FROM $nginx_version as stage2