def parse_header(header, zmw_counter=None):
    """
    >>> parse_header('>mine foo bar', 1)
    ('mine', 1, 'foo bar', 2)
    >>> parse_header('>mine/123/5_75 foo bar')
    ('mine', 123, '5_75 foo bar', None)

    For now, ignore the zmw and instead use a global counter.
    """
    if '/' in header:
        parts = header[1:].split('/')
    else:
        parts = header[1:].split(None, 1)
    movie = parts[0]
    if zmw_counter is None:
        zmw = int(parts[1])
    else:
        zmw = zmw_counter
        zmw_counter += 1
    if len(parts) > 1:
        extra = parts[-1]
    else:
        extra = ''
    return movie, zmw, extra, zmw_counter