Pattern Finding Software for text document information

I would like to know of or write a program that can find patterns for me. eg, in the list with the key character to find patters for as 1u: 3d,2a,1u,3a,4d,3a,1u,2a,3d,2a,1u,4d,3a,1u there are two occurences of 4d,3a,1u there is also two occurences of 1u two after 3d. The list will be long in reality and therefore I wish to use a program so I don't miss anything. Can anyone help with this? thanks in advance :)