ref: 23b63e6c9668efb47e01ebfca03b0aed5cbbe327
dir: /test/t.sub0/
{sub(/[aeiou]/, "foo"); print}
{sub("[aeiou]", "foo"); print}
{gsub(/[aeiou]/, "foo"); print}
{gsub("[aeiou]", "foo"); print}
{sub(/[aeiou]/, "&foo"); print}
{sub("[aeiou]", "&foo"); print}
{gsub(/[aeiou]/, "&foo"); print}
{gsub("[aeiou]", "&foo"); print}
{sub(/[aeiou]/, "\&foo"); print}
{sub("[aeiou]", "\&foo"); print}
{gsub(/[aeiou]/, "\&foo"); print}
{gsub("[aeiou]", "\&foo"); print}