Splitting out a file name in an image sequence from a directory path using tcl in Nuke

I'm writing this down, mostly so I won't have to dig around different nuke comps the next time I need it.  Using tcl to write little scripts in Nuke is very helpful, but it's a bit of an old language (just a few years younger than Perl), so it's got an interesting nomenclature.

Anyways I use this bit of tcl in my nuke text nodes to get the name of an image sequence:
 

[split [lindex [split [lindex [split [knob [topnode].file] "/"] 10] "."] 0] "_"] It first splits the whole path (which in this case has 10 tokens) using a "/" The last token is returned and split again based on "." And finally it splits out the last token if there's any underscores so a path like this: /job/thingny/dev/sandbox/sandbox_iguerrer/work/iguerrer/maya/images/skinTestSmooth_backLeft.####.iff ends up being displayed as this: skinTestSmooth backLeft This assumes you have a read node as the top most node in the tree with the text node in the flow. I'd like to figure (using tcl --- python is a bit easier for me when it comes to text manipulation) how to get the total number of tokens in the first directory split where I'm using "/", and then feed the number to the rest of the expression. Further explorations! addenum --  check out this web site for lots of nuke tcl tips: http://thoughtvfx.blogspot.com/2012/12/nuke-tcl-tips.html