for this patternthe two characters match the single character if the period character is missing or is different characterit does not match this backslash escape sequence is used for variety of special characters in regular expressions you can use \to insert square bracket without starting character classand \to insert parenthesiswhich we'll later see is also special character more interestinglywe can also use the escape symbol followed by character to represent special characters such as newlines (\ )and tabs (\tfurthersome character classes can be represented more succinctly using escape strings\ represents whitespace characters\ represents lettersnumbersand underscoreand \ represents digit'(abc]matches pattern '\(abc\] amatches pattern '\ \ \ '\ ndoes not match pattern '\ \ \ ' nmatches pattern '\ \ \wmatching multiple characters with this informationwe can match most strings of known lengthbut most of the time we don' know how many characters to match inside pattern regular expressions can take care of thistoo we can modify pattern by appending one of several hard-to-remember punctuation symbols to match multiple characters the asterisk (*character says that the previous pattern can be matched zero or more times this probably sounds sillybut it' one of the most useful repetition characters before we explore whyconsider some silly examples to make sure we understand what it does'hellomatches pattern 'hel* 'heomatches pattern 'hel* 'helllllomatches pattern 'hel*osothe character in the pattern says that the previous pattern (the characteris optionaland if presentcan be repeated as many times as possible to match the pattern the rest of the characters (heand ohave to appear exactly once it' pretty rare to want to match single letter multiple timesbut it gets more interesting if we combine the asterisk with patterns that match multiple characters *for examplewill match any stringwhereas [ - ]matches any collection of lowercase wordsincluding the empty string