[14166] error @0.102147> [hit #336]request to GET / crashed: YAML Error: Invalid element in map
   Code: YAML_LOAD_ERR_BAD_MAP_ELEMENT
   Line: 315
   Document: 1
 at /opt/perl5.14/lib/site_perl/5.14.2/YAML/Loader.pm line 352. in /opt/perl5.14/lib/site_perl/5.14.2/Dancer/Handler.pm l. 98

##</code><code>##

...
      question:
        - "You can select more than one answer.\n"
e answer.\n"

##</code><code>##

sub flush {
    my $self         = shift;
    my $session_file = yaml_file( $self->id );

    open my $fh, '>', $session_file or die "Can't open '$session_file': $!\n";
    flock $fh, LOCK_EX or die "Can't lock file '$session_file': $!\n";
    set_file_mode($fh);
    print {$fh} YAML::Dump($self);
    close $fh or die "Can't close '$session_file': $!\n";

    return $self;
}

##</code><code>##

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

use Fcntl qw(:flock :DEFAULT);

my $pid = fork;
die "Cannot fork.\n" unless defined $pid;

if ($pid) {
    open my $parent, '>', 'tmp'       or die "open parent: $!";
    sleep 1;
    flock   $parent, LOCK_EX          or die "lock parent: $!";
    print  {$parent} "Parent\n";
    close   $parent                   or die "close parent: $!";

} else {
    open my $child, '>', 'tmp'        or die "open child: $!";
    flock   $child, LOCK_EX           or die "lock child: $!";

    # Longer than parent:
    print  {$child} "Child here...\n";
    close   $child                    or die "close child: $!";
}


##</code><code>##

open my $fh, '+<', $file or die "Can't open '$file': $!\n";
flock $fh, LOCK_EX or die "Can't lock file '$file': $!\n";
truncate $fh, 0;
print {$fh} $content;
close $fh or die "Can't close '$file': $!\n";

##</code><code>##

sub atomic_write {
    my ($path, $file, $data) = @_;
    my ($fh, $filename) = tempfile("tmpXXXXXXXXX", DIR => $path);
    set_file_mode($fh);
    print $fh $data;
    close $fh or die "Can't close '$file': $!\n";
    rename($filename, $file) or die "Can't move '$filename' to '$file'";
}