#!/usr/bin/perl
use warnings;
use strict;
use IO::Handle;

$|++;
pipe( PARENT_READER, CHILD_WRITER );
pipe( CHILD_READER,  PARENT_WRITER );
PARENT_WRITER->autoflush(1);
CHILD_WRITER->autoflush(1);

my $pid;
if ( $pid = fork() ) {
    close(CHILD_READER);
    close(CHILD_WRITER);
    my $buffer;
    print PARENT_WRITER 1;
    while (1) {
        sysread( PARENT_READER, $buffer, 100 );
        print "parent revd: $buffer, and reply with ", $buffer + 1, "\
+n";
        sleep(1);
        print PARENT_WRITER $buffer + 1;
    }
}
else {
    close(PARENT_READER);
    close(PARENT_WRITER);
    my $buffer;
    while (1) {
        sysread( CHILD_READER, $buffer, 1000 );
        print "child revd: $buffer, and reply with ", $buffer + 1, "\n
+";
        sleep(1);
        print CHILD_WRITER $buffer + 1;
    }
}


##</code><code>##

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

my $pid = open(CHILD, "-|");

if ($pid)
{
   # parent
   print "parent got:\n";
   print while(<CHILD>);
   close CHILD; # this waits on child
}
elsif ($pid == 0)
{
   # child
   print "kid here!\n";
   exec '/bin/date' or die "Can't exec date $!\n";
}
else
{
   die "fork error: $!\n";
}