Fortinet 5.0 Patch 6 What are back-references?

Fortinet 678 FortiWeb 5.0 Patch 6 Administration Guide
See also
•What are back-references?
•Cookbook regular expressions
•Language support
•Rewriting & redirecting
•Defining custom data leak & attack signatures
•Configuring URL interpreters
•Configuring custom suspicious request URLs
What are back-references?
A back-reference is a regular expression token such as $0 or $1 that refers to whatever part of
the text was matched by the capture group in that position within the regular expression.
Back-references are used whenever you want the output/interpretation to resemble the original
match: they insert a substring of the original matching text. Like other regular expression
features, back-references help to ensure that you do not have to maintain a large, cumbersome
{} Quantifies the number of times the previous
character or capture group may be repeated
continuously.
To define a varying number repetitions, delimit it
with a comma.
Text : 1234567890
Regular expression: \d{3}
Matches: 123
Text : www.example.com
Regular expression: w{1,4}
Matches: www
If the string were a typo such as
“ww ” or “wwww”, it would also
match that.
Table 61:Popular FortiWeb regular expression syntax
Notation Function Sample Matches