regex to validate yahoo! IM accounts

[AliasZero]

From what I understand, a yahoo IM account can be made up of a-z A-Z 0-9 as well as . _ and -

Now i'm trying to write a regex to validate this:

/^{[_-0-9a-zA-Z\s]+$/} is what I have so far

It works fine, however the user should not be allowed to enter -- in the name, to stop a SQL injection exploit.

Does anyone know how I would go about allowing - but not --?

Thanks 😃