title: Checking strings with regex in C++
body: <p>I am going to use regular expressions in a C++ application, but I am not experienced in regex. I want in particular to check a number of strings if they belong to one of the following categories:</p>
  
  <p>X.anystring -> X must be necessarily and exclusively letter (not digit).</p>
  
  <p>XY.anystring -> X, Y must be necessarily and exclusively digits 0-9 (not letters).</p>
  
  <p>How can I check them using regex? What tutorial for regex could you recommend in order to acquaint me with regex?</p>