Select Code to Download

col1 col2 col3 col4 col5
1234 5678 9012 3456 7890

col1 col2 cYl2 col3 col4 col5
1234 5678 5Y78 9012 3456 7890

use strict;
use warnings;
...
        $line =~ s/(.{11}).(.*)/$1Y$2/;
        print $line."\n";
}