Syntax: zero or more regular expressions (REX), each on a separate line
Excludes URLs matching any of the specified regular expressions anywhere in the URL (hostname, path, or query).
| REX | Matches | 
| /scratch[0-9]/ | a subdirectory named scratch followed by a single digit | 
| [^\alnum]test[^\alnum] | the word test (but not retest or tester etc.) | 
See also Exclusions 3.4.8, Exclusion
prefix 3.5.24 and Exclude by Field 3.5.26.
See here for details on REX search syntax.