Programming Perl, 4th Edition

Character Classes

In a pattern match, you may match any character that has—or that does not have—a particular property. There are four ways to specify character classes. You may specify a character class in the traditional way, using square brackets and enumerating the possible characters, or you may use any of three mnemonic shortcuts: classic Perl classes like \w, using properties like \p{word}, or using legacy POSIX classes like [:word:]. Each of these shortcuts matches only one character from its set. Quantify them to match larger expanses, such as \d+ to match one or more digits. (An easy mistake is to think that \w matches a word. Use \w+ to match a word — provided by “word” you mean a programming language identifier with underscores and digits and such, not an English-language word.)