import re


def check_pre_release(tag_name):
    """
    Check the given tag to determine if it is a release tag, that is, whether it
    is of the form rX.Y.Z.  Tags that do not match (e.g., because they are
    suffixed with someting like -beta# or -rc#) are considered pre-release tags.
    Note that this assumes that the tag name has been validated to ensure that
    it starts with something like rX.Y.Z and nothing else.
    """

    release_re = re.compile('^r[0-9]+\\.[0-9]+\\.[0-9]+')

    return False if release_re.match(tag_name) else True