You can put a set of literal characters inside square brackets, proceeded by a circumflex (^). The pattern matches only if none of the set of characters is found.
Regular Expression
Match
Not a Match
a[^bcd]ef
axef, akef
abef, acef, adef, axkef
a[^b-d]ef
file[^1-2][0-9]?
file3, file45
file, file1, file10