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
Learn how to use regular expressions with Tcl’s regexp and regsub commands| www.regular-expressions.info
In a regular expression, POSIX bracket expressions can be used to match one of a certain kind of characters.| www.regular-expressions.info