Formula To Extract All Characters After A Certain Number Of Forward Slashes From The Right?

I'm working with a large list of items of varying length. A sample worksheet is attached. I need to do the following:

1) If the characters after the final forward slash from the right are of the pattern "tttxxx" (where "t" is text and "x" is a number/digit), then return all characters to the right of the final slash, including the slash itself:

Y:/Series/hun/hun109 ----> /hun109

2) if the characters after the final slash from the right are not of the pattern "tttxxx", then return all characters after the second slash from the right, including the slash:

Z:/Series/crd/crd409/editorial ----> /crd409/editorial

3) if there are less than 3 backslashes in the item, return a blank.