Sometimes it is necessary to place wildcards in the command line without having the shell treat them as special characters. This can be done by either preceding a single wildcard character with a backslash, \<\tt>, or enclosing a sequence of wildcard characters in apostrophes, ' '.
For example, if you wanted to set your C shell prompt to a question mark and typed
set prompt=?
the question mark would be expanded to be the first single-character
filename in the working directory. If one exists it will be your prompt.
If no single-character filenames exist, you will get a ``set: No match''
error. You should have typed
set prompt=\?