pattern matching syntax Syntax Description \0 NUL \t Tab \n newline \w [a-zA-Z0-9_] \W [^a-zA-Z0-9_] \s empty space \S NOT empty space \d [0-9] \D [^0-9] {min,max} min and max occurences {min,} min occurences {n} n occurences {n}? not greedy ^ string start $ end string