"Header1","Header2",Header3"
"A123","1","valueB1"
"B234","1","valueB2"
"C345","2","valueB3"
"D456","3","valueB4"
"E567","4","valueB5"
"F678","5","valueB6"

##</code><code>##

"Header1","Header2",Header3"
"A123","P","valueB1"
"B234","P","valueB2"
"C345","1","valueB3"
"D456","2","valueB4"
"E567","3","valueB5"
"F678","4","valueB6"

##</code><code>##

open my $fh1,'<',"NRoomch.txt";
my @a = <$fh1>; 
my @arr;
 for  $i (0..$#a){
  my @b = split(/,/,$a[$i]);
    for $j (0..$#b) {
        $b[$j] =s~/"//g;
if ($j==1 && my @arr = grep { $_ =~ /\"1"$/ } @b);
        @arr = map{$_ = "P"} @arr;            
        else
        @arr = map {$b[$j] - 1} (1..$#b);
        print @arr;
    };
 };
close($fh1);