use IO::Handle;
use IO::Select;

my %pids;    # kid job description keyed on pid
my $kids_fh; # pipe filehandles foreach kid keyed on fileno

my $rset = IO::Select->new;
local $| = 1;

local $SIG{CHLD} = sub {
    my $waitedpid = wait;
    print "process $waitedpid ($pids{$waitedpid}) finished" if $waitedpid > 0;
};

# spawn childeren

for my $cmd( @cmds ) {
    ;
    my ($rh,$wh);
    for ($rh,$wh) {
        $_ = IO::Handle->new;
        $_->autoflush;
    }
    pipe($rh,$wh);

    if ((my $pid = fork) == 0) {
        # child code
    } else {
        # parent
        $rset->add($rh);
        $pids{$pid} = $cmd;
        $kids_fh{fileno($rh)} = $pid;
    }
}

# now interact with kids

while(1) {
    last unless $rset->handles;
    foreach my $rh (sort { fileno $a <=> fileno $b } $rset->can_read) {
        my $response = do { local $/; <$rh> };
        ...
        ...
        $rset->remove($rh);
    }
}