cl-ppcre:split question

The examples for cl-ppcre:split here

http://weitz.de/cl-ppcre/#split

include this tempting recipe:

(split "\s+" "foo bar baz frob")

=> ("foo" "bar" "baz" "frob")

However,

(split "\s+" " foo bar baz frob")

=> ("" "foo" "bar" "baz" "frob")

I.e., the result list includes an empty string as the first element if there are one or more whitespace characters at the beginning of the string.

How can I get rid of the empty string at the beginning? Is there a regexp match for this that would work with split?

Thanks,

Mark