warn 'tab' unless unescape("\\t")  eq "\t";   #works
   warn 'nl'  unless unescape("\\n")  eq "\n";   #fails
   warn 'bel' unless unescape("\\07") eq "\07";  #fails

   sub unescape
   {
      my($s)=@_;

      $s =~ s/(\\[^\d])/$1/ge;  #"\t", "\n", etc.
      $s =~ s/(\\0\d+)/$1/ge;   #"\07", etc.

      return $s;
   }