Inject variables into a homebrew formula.
f='() {eval "$(echo "cat <<EOF\\n$(cat $1)\\nEOF")"}' \
version=\$(grep "# @version" foo | cut -d ' ' -f 3) \
website=\$(grep "# @website" foo | cut -d ' ' -f 3) \
sha256=\$(shasum -a 256 foo | cut -d ' ' -f 1) \
eval $f formula > foo.rb