If I understand you, you want to enumerate each occurrance of the first column of your data (the alphabetic letter). Maybe something like: 
my %sequence;
while (<>) {
  my @line = split;
  my $sequence = ++$sequence{$line[0]};
  print "@line $sequence\n";
}

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-- Randal L. Schwartz, Perl hacker
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In reply to Re: Generating sequence nos. for data by merlyn
in thread Generating sequence nos. for data by icg

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