Form validation regex_match

[eluser]Perkin5[/eluser]
I want a form field to match this regex:

[a-zA-Z]\s

which I believe should match any alphabetical character or whitespace character and I am using it as follows:

Code:

$this->form_validation->set_rules('name','Name','required|regex_match[[a-zA-Z]|\s]|xss_clean');

but it does not work correctly. With a purely alphabetical string in the input field I get the error message: The Name field is not in the correct format.

What am I doing wrong?