#!/usr/bin/perl

use strict; # https://perlmonks.org/?node_id=11160631
use warnings;

my $save_fn = 'save.fn'; # NOTE

my @c_speed = (5, 8, 12, 8);
my $sfh;
  open($sfh, '>', $save_fn) or
        die "Unable to open file $save_fn : $!";
  print $sfh "@c_speed\n";
  close $sfh; # NOTE

#...
#
#The file contains a line that looks like "5 8 12 8\n"
#...

my $load_fn = 'save.fn'; # NOTE

my $lfh;
  open($lfh, '<', $load_fn) or
        die "Unable to open file $load_fn : $!";
#$rstring  = <$lfh>;  # Char speeds
#  ($c_speed[0], $c_speed[1], $c_speed[2], $c_speed[3]) = sscanf("%d %d %d %d", $rstring);
  # NOTE using ' ' instead of / / also removes the \n
  @c_speed = map $_ + 0, split ' ', <$lfh>; # NOTE force number

use Data::Dump 'dd'; dd @c_speed;