Regexp Format help

Hi,

I am setting up a site which uses single session for joomla and moodle. I want to validate usernames for easysocial compatible with moodle, moodle doesn't allow spaces in username but easysocial does, which creates error. I want easysocial to accept only alphanumeric values and hyphen, underscore or period (-/_/.).

I have attached moodle allowed characters description and my easysocial regexp settings screenshot, registration form screenshot as its not validating as I think.

Any help or suggestion?