| Alternate Matching and Grouping of Expressions:
| Alternation Separates alternates, often used with grouping operator ()
( ) Group Groups subexpression into a unit for alternations, for quantifiers, or for backreferencing
[char] Character list Indicates a character list;
Most metacharacters inside a character list are understood as literals,with the exception of character classes, and the ^ and - metacharacters
Oracle's regular expression implementation supports the POSIX (Portable Operating System Interface) character classes as shown below:
[:alpha:] Alphabetic characters
[:lower:] Lowercase alphabetic characters
[:upper:] Uppercase alphabetic characters
[:digit:] Numeric digits
[:alnum:] Alphanumeric characters
[:space:] Space characters (nonprinting), such as carriage return, newline, vertical tab, and form feed
[:punct:] Punctuation characters
[:cntrl:] Control characters (nonprinting)
[:print:] Printable characters
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