This section describes the basics of regular expression patterns, which are found in all versions of Tcl. There are occasional references to features added by advanced regular expressions, but they are covered in more detail starting on page 138. There is enough syntax in regular expressions that there are five tables that summarize all the options. These tables appear together starting at page 145.
A regular expression is a sequence of the following items:
A literal character.
A matching character, character set, or character class.
A repetition quantifier.
An alternation clause.
A subpattern grouped with parentheses.
Most characters simply match themselves. The following pattern matches an a followed ...