True allergies to cow's milk are relatively uncommon. Only 2 to 3 percent of children are allergic to milk, according to the AAP, and almost all of them outgrow it by age 3. (Learn the difference between a milk allergy and lactose intolerance .).
The underscore [ _ ] (also called underline, underbar, low line, or low dash) is a character that originally appeared on the typewriter and was primarily used to underline words.
Details: 1  The \w means any word character which usually means alphanumeric (letters, numbers, regardless of case) plus underscore 2  (_) The ^ anchors to the beginning of a string, and the $ anchors. 3  The [] means a character class, which means match any character contained in the character class.