# server.pl
use strict;
use warnings;

use POSIX ();

my $cgis = 0;

$SIG{CHLD} = sub {
    while ( waitpid( -1, POSIX::WNOHANG ) > 0 ) {
        $cgis -= 1;
    }
};

while (1) {
    print '(Ctrl-D to quit)> ';
    my $request = <STDIN>;
    last if not defined $request;
    chomp $request;

    print "Server: about to fork a CGI client\n";

    $ENV{foo} = 'bar';     # use some real
    $ENV{baz} = 'quux';    # CGI variables

    pipe my ( $child_stdin,       $input_to_child, );
    pipe my ( $output_from_child, $child_stdout, );

    my $pid = fork;

    if ( $pid == 0 ) {
        close $input_to_child;
        close $output_from_child;

        open STDIN,  '<&', $child_stdin;
        open STDOUT, '>&', $child_stdout;
        exec {'perl'} 'perl', 'client.pl';
    }
    else {
        close $child_stdin;
        close $child_stdout;

        print "Server: forked process $pid\n";

        $cgis += 1;

        print $input_to_child $request;
        close $input_to_child;
        print
          "Server: reading child response\n",
          <$output_from_child>;
    }
}

print "Server exiting, remaining children: $cgis\n";

##</code><code>##

# client.pl

use strict;
use warnings;

my $input = <STDIN>;

print <<END

This is a pseudo-CGI client reporting.
Process number $$
Got input "$input"
\$ENV{foo} is "$ENV{foo}"
\$ENV{baz} is "$ENV{baz}"
End of report

END