{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}