my $infile  = "/tmp/foo.in";
my $outfile = "/tmp/foo.out";
my $binary  = "./output.pl";

system("mkfifo $infile");
system("$binary < $infile > $outfile &");

open(DATA_OUT, ">$infile");
open(DATA_IN, "<$outfile");

while($line = <DATA_IN>) {
    chomp $line;
    print "Got $line\n";

    if ($line =~ /\?/) {
        print DATA_OUT, "blah\n";
    }
}

close(DATA_OUT);
close(DATA_IN);

system("rm $infile $outfile");