You can use meta-characters in the 'Search For' field:

|. |any character except newline |+ |one or more times
|* |zero or more times |? |zero or one time
|{n} |match exact n times |{n,m} |at least n, at most m times
|~| |pipe: {{a~|b}} matches a or b | - |hyphen, match a range of chars
|^ |beginning of a line |$ |end of a line
|[[...] |one of the char's of a set |[[^...] |negated character set
|\b |word boundary |\B |word non boundary
|\d |numeral [[0-9] |\D |non numeral [[^0-9]
|\s |single white space |\S |single non white space
|\w |[[A-Za-z0-9_] |\W |[[^A-Za-z0-9_]
|(...) |grouping are stored as $1..$9 |\. |escape a meta char

The 'Replace with' field can use $1..$9 as a backreference to parentheses of 'Search for' field.
----
Example:\\

Search for __/abc|def/__ will match the word 'abc' or the word 'def'\\
Search for __/bwiki/b__ will match the word 'wiki' but not the word 'jspwiki'.\\
Search for __^[[IVXMDCL]+\.__ will match any combination of roman numeral char's followed by a period\\
Search for __/(-?\d+)(\d{3})/__ and replace with __$1,$2__ to insert commas in large integers.

This is the [EditFindAndReplaceHelp] page.
[More info on regular expressions|http://www.regular-expressions.info/javascript.html],
JavaRegularExpressions, and [RegExp Sandbox|http://www.regular-expressions.info/javascriptexample.html]\\