#!/usr/bin/perl

tie *STDOUT, TrapClass;

my $pid = fork();
die "" if !defined $pid;
exit 0 if $pid; # parent exits

my $tied_descr = fileno(STDOUT);
exec "/bin/date >&$tied_descr"; # child

package TrapClass;

use Fcntl qw(F_GETFD F_SETFD FD_CLOEXEC);

sub TIEHANDLE {
    my $class = shift;
    open(my $fh, ">out") or die;
    
    my $flags = fcntl($fh, F_GETFD, 0) or die "Can't get flags: $!\n";
    # clear close-on-exec flag
    fcntl($fh, F_SETFD, $flags & ~FD_CLOEXEC) or die "Can't set flags: $!\n";

    bless { fh => $fh }, $class;
}

sub PRINT {
    my $self = shift;
    my $fh = $self->{fh};
    print $fh @_;
}

sub FILENO {
    my $self = shift;
    my $fh = $self->{fh};
    return fileno($fh);
}