CONTENTS

• NAME
• DESCRIPTION
  • The dot
  • Backslash sequences
    • \N
    • Digits
    • Word characters
    • Whitespace
    • Unicode Properties
      • Examples
  • Bracketed Character Classes
    • Special Characters Inside a Bracketed Character Class
    • Character Ranges
    • Negation
    • Backslash Sequences
    • POSIX Character Classes
      • Negation of POSIX character classes
      • [= =] and [. .]
      • Examples
    • Extended Bracketed Character Classes

#NAME

perlrecharclass - Perl Regular Expression Character Classes

#DESCRIPTION

The top level documentation about Perl regular expressions is found in perlre.

This manual page discusses the syntax and use of character classes in Perl regular expressions.

A character class is a way of denoting a set of characters in such a way that one character of the set is matched. It's important to remember that: matching a character class consumes exactly one character in the source string. (The source string is the string the regular expression is matched against.)

There are three types of character classes in Perl regular expressions: the dot, backslash sequences, and the form enclosed in square brackets. Keep in mind, though, that often the term "character class" is used to mean just the bracketed form. Certainly, most Perl documentation does that.

#The dot

The dot (or period), . is probably the most used, and certainly the most well-known character class. By default, a dot matches any character, except for the newline. That default can be changed to add matching the newline by using the single line modifier: either for the entire regular expression with the /s modifier, or locally with (?s). (The "\N" backslash sequence, described below, matches any character except newline without regard to the single line modifier.)

Here are some examples:

"a"  =~  /./       # Match
"."  =~  /./       # Match
""   =~  /./       # No match (dot has to match a character)
"\n" =~  /./       # No match (dot does not match a newline)
"\n" =~  /./s      # Match (global 'single line' modifier)
"\n" =~  /(?s:.)/  # Match (local 'single line' modifier)
"ab" =~  /^.$/     # No match (dot matches one character)

#Backslash sequences

A backslash sequence is a sequence of characters, the first one of which is a backslash. Perl ascribes special meaning to many such sequences, and some of these are character classes. That is, they match a single character each, provided that the character belongs to the specific set of characters defined by the sequence.

Here's a list of the backslash sequences that are character classes. They are discussed in more detail below. (For the backslash sequences that aren't character classes, see