Regex error 'missing terminating ] for character class at offset 8'

select count(gc_ads.n) from gc_ads,gc_index where ( (t1<=1711621903 OR t1=0) AND (t2>=1711621903 OR t2=0) AND status = 'enabled' AND x_paypal_disabled = '0' ) and ((gc_index.all_text REGEXP '[Perfect')) AND gc_ads.n = gc_index.n