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

my $save_fn = 'colintu.dat';
my @c_speed = (5, 8, 12, 8);

open my $sfh, '>', $save_fn or
        die "Unable to open file $save_fn : $!";
print $sfh "@c_speed\n";
close $sfh;

open my $lfh, '<', $save_fn or
    die "Unable to open file $save_fn : $!";
@c_speed = split / /, <$lfh>;
print "Have: @c_speed\n";

@c_speed = map { $_ * 2 } @c_speed;
print "Doubled: @c_speed\n";

close $lfh;
unlink $save_fn; # clean up