Character class abbreviations allow you to match any of a set of characters without too much hassle.
One way to do this is to put the set of characters you want to match from within .
For instance  would allow you to match any of those numbers. This can be
kind of cumbersome. You can also negate a character class by placing a caret at the front of it. For
instance [^0123456789] matches anything that is not a number. You shouldn't be surprised that Perl makes your life much easier by
defining some character class a bbreviations. These are alphanumeric characters preceded by a
backslash. Perl allows you to match any number with a \d in your regular expression.
Now for a quick word about metacharacters. Metacharacters are characters that have special meaning within regular
expressions. Therefore if you put them into a regular expression they won't match literally. Unless you precede the
metacharacter with a \. The metacharacters are \|()$^.?* Now for a quick word about each of them do before
we return to character class abbreviations.
|.||Matches any character besides newline|
|()||Used for grouping characters|
|||Used for defining character classes|
||||Used for or in regular expression|
|\||Denotes the beginning of a character class abbreviation, or for the following metacharacter to be matched literally|
|*||Quantifier matches 0 or more of the previous character or group of characters|
|?||Makes a quantifier nongreedy|
|^||Matches the beginning of a string (or line if /m is used)|
|$||Matches the end of a string (or line if /m is used)|
Now lets define some character classes
|\d||digit or |
|\D||nondigit or [^0123456789]|
|\w||word (alphanumeric) or [a-zA-Z_0-9]|
|\s||whitespace character [ \t\r\n\f]|
|\S||non whitespace character|
That's a lot of information to get a handle on. So lets check out pattern-matching examples