In a regular expression, the question mark makes the preceding token optional.| www.regular-expressions.info
In a regular expression, square brackets are used to indicate character classes, which matches any of the characters in the character set.| www.regular-expressions.info
In a regular expression, the asterisk or star causes the preceding token to be matched zero or more times, and the plus one or more times.| www.regular-expressions.info
In a regular expression, the vertical bar or pipe symbol tells the regex engine to match any of two or more options| www.regular-expressions.info
Named Capturing Groups and Backreferences| www.regular-expressions.info
In a regular expression, parentheses can be used to group regex tokens together and for creating backreferences. Backreferences allow you to reuse part of the regex match in the regex, or in the replacement text.| www.regular-expressions.info
Numbered Backreferences| www.regular-expressions.info
In a regular expression, parentheses can be used to group regex tokens together and for creating backreferences. Backreferences allow you to reuse part of the regex match in the regex, or in the replacement text.| www.regular-expressions.info
If you have written regular expressions before, you know that the regex syntax can be hard to keep track of. Certainly when writing a regex pattern that uses plenty of grouping and alternation.| www.regexbuddy.com