I never cease to be amazed at the number of different ways that data can be encoded into simple test lines ... and how the various languages that we teach can be used to manipulate / extract pertinent information. Today, on a Tcl Course, I was presented with data in this form:
  T/N/R/Brother/Sister/Mum/Bob.txt/Esmerelda.txt/Sophie.txt

The first three fields can be disregarded. The rest of the line lists a series of relationships (and unspecified number from 0 up) followed by a series of file names, each of which relates to a relationship. Nothing nice like them being in pairs on the line - it's all the relationships followed by all the file names.

Solution?
 1. Reformat the line into a list with split
 2. Calculate the number of relationships with expr
 3. Loop (a for loop) through each relationship
 4. In the loop, calculate positions of the relationship and file name with expr
 5. Extract the field you want with lindex
Complete source code example [here]
(written 2011-05-10)

 T206 - Tcl/Tk - Lists
  [144] Tcl sandwich - lists in Tcl - (2004-12-08)
  [463] Splitting the difference - (2005-10-13)
  [781] Tcl - lappend v concat - (2006-06-27)
  [1282] Stringing together Tcl scripts - (2007-07-29)
  [1283] Generating traffic for network testing - (2007-07-29)
  [1334] Stable sorting - Tcl, Perl and others - (2007-09-06)
  [1402] Tcl - append v lappend v concat - (2007-10-23)
  [1405] Sorting in Tcl - lists and arrays - (2007-10-24)
  [1601] Replacing the last comma with an and - (2008-04-04)
  [2468] What are Tcl lists? - (2009-10-22)
  [2472] split and join in tcl and expect - (2009-10-23)
  [3394] The difference between lists and strings - Tcl - (2011-08-16)
  [3415] User defined sorting and other uses of callbacks in Tcl and Tk - (2011-09-02)
  [3582] Tcl collections - lists, dicts and array - (2012-01-16)
  [3583] Expanding a list of parameters in Tcl - {*} and eval - (2012-01-17)
  [3618] lists and struct::list in Tcl - Introduction to struct::list and examples - (2012-02-18)
  [4209] Lists in Tcl - fundamentals in a commented source code example - (2013-11-16)
  [4454] Everything is a string - even a list - (2015-03-11)
  [4455] Working out distance between places, using OS grid references and a program in Tcl - (2015-03-11)

T205 - Tcl/Tk - String Handling in Tcl
  [404] How to check that a string contains a number in Tcl - (2005-08-06)
  [779] The fragility of pancakes - and better structures - (2006-06-26)
  [943] Matching within multiline strings, and ignoring case in regular expressions - (2006-11-25)
  [1403] Square Bracket protection in Tcl - (2007-10-23)
  [1410] Tcl / regsub - changing a string and using interesting bits - (2007-10-27)
  [3192] Tcl - Some example of HOW TO in handling data files and formats - (2011-03-04)
  [3576] Tcl - apparently odd behaviour of string trimleft - (2012-01-13)
  [4205] Regular Expression Substitution - Tcl - (2013-11-12)

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