##
$output=`more datafile`;
##
##
$pid=open READER, "programname arguments|" or die "Can't run the program: $!\n";
while(){
$output.=$_;
}
close READER;
##
##
$pid=open WRITETOME, "|programname arguments" or die "Couldn't fork process";
print WRITETOME "write this\n";
close WRITETOME;