title: How to increment/Decrement the Alpabetic letters in indexing titles
body: <p>I have a Input text with delimit by tab A - Z series (number and text)</p>
  
  <p>Inputfile.csv:</p>
  
  <pre><code>16  ASeries titles
  49  ASeries titles
  102 ASeries titles
  167 BSeries titles
  198 BSeries titles
      ...........
  178 WSeries titles
  187 WSeries titles
  187 ZSeries titles
  </code></pre>
  
  <p>Output text should be:</p>
  
  <pre><code>&lt;A&gt;
  16  ASeries titles
  49  ASeries titles
  102 ASeries titles
  &lt;/A&gt;
  
  &lt;B&gt;
  167 BSeries titles
  198 BSeries titles
  &lt;/B&gt;
  ...........
  &lt;W&gt;
  178 WSeries titles
  187 WSeries titles
  &lt;/W&gt;
  &lt;Z&gt;
  187 ZSeries titles
  &lt;/Z&gt;
  </code></pre>
  
  <p>The problem is whenever the alphabetic sequence is missing (X and Y) the output is collapsed.</p>
  
  <p>My Code:</p>
  
  <pre><code>use strict;
  use warnings;
  
  my $csvcnt = "";
  readString( "Inputfile.csv", \$csvcnt );
  
  my @_alp = qw(A B C D E F G H I J K L M N O P Q R S T U V W X Y Z);
  
  #$csvcnt = $alp."_starts\n".$csvcnt;
  for ( 0 .. 25 ) {
     if ( $csvcnt !~ m/\n\d+\t$_alp[$_]/i ) {
        pop @_alp, $_alp[$_];
        next;
     }
     if ( $_ &gt; 0 ) {
        $csvcnt =~ s/\n\d+\t$_alp[$_]/\n&lt;\/$_alp[$_-1]&gt;\n&lt;$_alp[$_]&gt;$&amp;/i;
     }
     elsif ( $_alp[$_] == 'Z' ) {
        $csvcnt =~ s/\n\d+\t$_alp[$_]/\n&lt;$_alp[$_]&gt;\n$&amp;\n&lt;\/$_alp[$_-1]&gt;/i;
     }
  }
  
  
  #----------------&gt;
  sub readString    #Readfile in Strings
  
    #----------------&gt;
  {
     my $File   = shift;
     my $string = shift;
     open( FILE1, "&lt;$File" )
       or die "\nFailed Reading File [$File]\n\tReason: $!";
     read( FILE1, $$string, -s $File, 0 );
     close(FILE1);
  }
  </code></pre>
  
  <p>It would be appreciate if anybody could help me on this.</p>