There are a few base behavior differences from standard regular expression usage to match the functionality of the Windows filesystem and Windows registry:
- All characters are in Unicode
- A character is considered to be in a set if either its lower case format or its upper case format is in the set, i.e. all character comparison is done case insensitively.
- ^ is prepended and $ appended to all the regular expressions so they must match the entire string, not a substring.
The syntax supported by Application and Device Control is listed here:
- Character : Matches itself, unless it is a special character (metachar): . \ [ ] * + ^ $
- . : Matches any character.
- \ : Matches the character following it, except when followed by a left or right round bracket, a digit 1 to 9 or a left or right angle bracket. (see ,,). It is used as an escape character for all other meta-characters, and itself. When used in a set (), it is treated as an ordinary character.
- [set] : Matches one of the characters in the set. If the first character in the set is "^", it matches a character NOT in the set, i.e. complements the set. A shorthand S-E is used to specify a set of characters S up to E, inclusive. The special characters "]" and "-" have no special meaning if they appear as the first chars in the set.
- * : Any regular expression form  to  followed by closure character (*) matches zero or more matches of that form.
- + : Same as , except it matches one or more.
- A regular expression in the form  to , enclosed as \(form\) matches what form matches. The enclosure creates a set of tags, used for  and for pattern substitution. The tagged forms are numbered starting from 1.
- A \ followed by a digit 1 to 9 matches whatever a previously tagged regular expression () matched.
- \< \> : A regular expression starting with a \<construct> construct, restricts the pattern matching to the beginning of a word, and/or the end of a word. A word is defined to be a character string beginning and/or ending with the characters A-Z a-z 0-9 and _. It must also be preceded and/or followed by any character outside those mentioned.
- A composite regular expression xy where x and y are in the form  to  matches the longest match of x followed by a match for y.
- ^ $ : A regular expression starting with a ^ character and/or ending with a $ character, restricts the pattern matching to the beginning of the line, or the end of line [anchors]. Elsewhere in the pattern, ^ and $ are treated as ordinary characters.