How to Find or Validate an Email Address| 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
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
Learn how to use regular expressions with Tcl’s regexp and regsub commands| www.regular-expressions.info
In regular expressions, \b anchors the regex at a word boundary or the position between a word and a non-word character, or vice versa.| www.regular-expressions.info
Test for a match, or test for failure, without actually consuming any characters.| www.regular-expressions.info