<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _merge(*args):
 """Create a composite pattern and compile it."""

    return re.compile(r'^' + r'[/-]'.join(args) + r'(?:\s+' + _dow + ')?$')