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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:

def set_(name, add, match):
    '''
    Add a value to the named set

    USAGE:

    .. code-block:: yaml

        foo:
          reg.set:
            - add: bar
            - match: my/custom/event
    '''
    ret = {'name': name,
           'changes': {},
           'comment': '',
           'result': True}
    if name not in __reg__:
        __reg__[name] = {}
        __reg__[name]['val'] = set()
    for event in __events__:
        if salt.utils.stringutils.expr_match(event['tag'], match):
            try:
                val = event['data']['data'].get(add)
            except KeyError:
                val = event['data'].get(add)
            if val is None:
                val = 'None'
            ret['changes'][add] = val
            __reg__[name]['val'].add(val)
    return ret