[a-zA-Z] is included in [Azizz]
uppercase A in the code table 65 Z is 90 a is 97 z and so on

this is based on the ASSIC code table. Amurz corresponds to 97122 , Amurz corresponds to 65-90 , of course Amurz corresponds to 65122 .
you will find that if you write [a-zA-Z] will not include 91-96 . These in turn represent [\] ^ -,
here is attached a search ASSIC code table link: http://tool.oschina.net/commo.