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Regular Expressions   «Prev  Next»
Lesson 3Regular expression reference
ObjectiveWrite a regular expression that will catch most common misspellings of your name.

Regular Expression Reference

Perl regular expressions are based on the standard egrep-style (so-called version 8) regexps. These regexes perform pattern matching based on a set of rules. The basic set of rules are explained in this lesson.
For the purpose of the examples in this discussion, we will use the simple form of Perl's pattern-matching

operator (m//): 

For a review on the matching operator, see "The match operator" lesson from Module 3.

Pattern- matching rules

There are a lot of details in this lesson that we will be using later on in the module. Be sure to read each of the sidebar pages linked from this lesson. In addition, we will apply the regular expressions discussed to the yes/no if structure we examined in the previous lesson.


  1. Any single character matches itself, unless it is one of the recognized metacharacters.
  2. You can also use special metacharacters to match the beginning or end of a line or string .
  3. Brackets are used to create your own class of characters.
  4. The backslash (\) character is used to create special escape characters for matching some nonalphanumerics and classes of characters.
  5. The period (.) matches any character (except \n). To match a period itself, use \. or [.].
  6. Alternate matches can be specified using | to separate them.
  7. Within a pattern, you can specify subpatterns for later reference by enclosing them in parenthesis. You can refer to those subpatterns later by using \n where the n refers back to the nth subpattern. These are called back-references.
  8. You can repeat a pattern several times by following a character, class, or parenthesized expression with one of these quantifiers.

Perl Spell Check Name - Exercise

Click the exercise link below to write a regular expression that will catch misspellings of your name.
Perl Spell Check Name - Exercise