use IPC::Open2;
use Symbol;

$WTR = gensym();  # get a reference to a typeglob
$RDR = gensym();  # and another one

$pid = open2($RDR, $WTR, 'bc');

while (<STDIN>) {            # read commands from user
     print $WTR $_;          # write a command to bc(1)
     $line = <$RDR>;         # read the output of bc(1)
     print STDOUT "$line";   # send the output to the user
}