use Data::Dumper;
$Data::Dumper::Terse = 1;
open (my $fh,'>','config.dat') or die $!;
print $fh Dumper(\%config);
close($fh);

open ($fh,'<','config.dat') or die $!;
my $config_neu;
{ 
$/ = undef;
my $s= <$fh>;
eval '$config_neu='.$s;
}
die $@ if $@;
print Dumper($config_neu);