...
 if($fName =~ /^([\[\(].+?[\]\)])/)
  {
    #pref detected. generalizing digits
      my $pref = '^\Q'.$1.'\E';
      $pref =~ s/\d++/\\E\\d++\\Q/g;
    #finding indexes of matches to this prefix
      my @matchIndexes;
      for(my $mex=0;$mex<@fNames;$mex++)
      {if($fNames[$mex] =~ /$pref/i){push(@matchIndexes,$mex);}}
    ...