#!/usr/bin/perl
use strict;
use warnings;

my $linesep_len = length($/);
my $rec_len = length('ACATCACCTCCCACAACGAGGACTACACCATCGTGGAACA') + $linesep_len;
my $read_len = 1;
my $skip_len = $rec_len - $read_len;

binmode(DATA);
seek(DATA, 10, 1) or die "seek error";
my $buf = ' ' x $read_len;
while (read(DATA, $buf, $read_len) > 0) {
    print $buf, "\n";
    seek(DATA, $skip_len, 1) or last;
}

__DATA__
ACATCACCTCCCACAACGAGGACTACACCATCGTGGAACA
ACATCACCTCxCACAACGAGGACTACACCATCGTGGAACA
ACATCACCTCsCACAACGAGGACTACACCATCGTGGAACA
ACATCACCTCjCACAACGAGGACTACACCATCGTGGAACA
ACATCACCTCcCACAACGAGGACTACACCATCGTGGAACA
ACATCACCTCCCACAACGAGGACTACACCATCGTGGAACA
ACATCACCTCCCACAACGAGGACTACACCATCGTGGAACA
ACATCACCTCCCACAACGAGGACTACACCATCGTGGAACA
ACATCACCTCCCACAACGAGGACTACACCATCGTGGAACA
ACATCACCTC-CACAACGAGGACTACACCATCGTGGAACA