#!/usr/bin/perl -w

    use strict;

    open FILE, 'reload.xls' or die "Error message here: $!";

    binmode FILE; # as required

    my $buffer = 4096;
    my $str;

    while (read FILE, $str, $buffer) {
        for (split //, $str, $buffer) {
            # Your code here
        }
    }