A possibility to specify the Array or Hash parameters for request string

Need a request params line like this
cust_num=945263&item_nums[NC12345]=3&item_nums[NC28521]=10

A hash 
{ cust_num:945263, item_nums: {NC12345: 3, NC28521: 10 } } 
was parsed like
cust_num=945263&item_nums=%7B%3ANC12345%3D%3E3%2C+%3ANC28521%3D%3E10%7D

The same problem was with arrays