Global Substitution regular expressions are implemented using Java.
You can create a Global Substitution rule that contains a regular expression in either the Find or Replace with fields. Select the RegEx check box to indicate the rule uses regular expressions.
Consult Java reference documentation for a full description of regular expressions. One source is on the Oracle website: http://docs.oracle.com/javase/6/docs/api/java/util/regex/Pattern.html#cg