Pardon my ignorance, but I have trouble understand the docs of IPC::run3

How do I implement the following, including catching stdout and stderr with run3?

the docs claim

compared to system(), qx'', open "...|", open "|..."

... BUT ...

Note that this form of redirecting the child's I/O doesn't imply any form of concurrency between parent and child - run3()'s method of operation is the same no matter which form of redirection you specify.

I'm confused, is it even possible to have a bidirectional communication between two simultaneously running processes with run3?

If not what's the appropriate solution?

client.pl

use v5.12;
use warnings;
use IPC::Run3;


my ($cmd, $in, $out, $err);

$cmd = 'perl ./server.pl';


open my $fh_in,"|-", $cmd;

#my @in;
#run3($cmd, \@in);

sub out {
    $fh_in->say(@_);
}


my $doit;

for my $try (2,3,2) {
    $doit = "$;" x $try;
    out($doit);
    out($_) for 1..$try;
    out($doit);
}

out("EOF");
[download]

server.pl

use v5.12;
use warnings;

STDOUT->autoflush;
my $doit;
my $input;

while ( my $line = <STDIN> ) {
    unless ( defined $doit ){
        $doit = $line;
        last if $doit eq "EOF";
        next;
    }

    if ($line eq "$doit") {
        doit();
        undef $doit;
    } else {
        $input .= $line;
    }
}

say "exit by $doit";
exit;

sub doit {
    print "((( STDOUT ::: $doit";
    print $input;
    print "))) STDOUT ::: $doit";
    #warn "STDERR:",$input," ";
    $input ="";
}
[download]

output

((( STDOUT ::: 
1
2
))) STDOUT ::: 
((( STDOUT ::: 
1
2
3
))) STDOUT ::: 
((( STDOUT ::: 
1
2
))) STDOUT ::: 
exit by EOF
[download]

update

found this

Bidirectional Communication with Another Process

doesn't seem to be overly portable and I doubt run3 is the solution...

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