just tried to run this script again on my newer linux system with a 2.6.x kernel and Perl 5.8.7. Anyways, there seems to be a difference in the way pipes work, and the above script no longer works. Below is another version that does work. It includes an output-to-file, so you can compare the output to bc running in a terminal.

#!/usr/bin/perl
use warnings;
use strict;
use IPC::Open3;
require 'sys/ioctl.ph';
use FileHandle; # for testing output to compare to 
                # bc's output, needed for autoflush 

$| = 1;

#to write to a file to compare to bc's output 
open (OUT, "> $0.out") or die "$!\n";
OUT->autoflush(1);

# I tested this with  
#  "q @ 2" to generate errors 
# "123^12345" to generate big output 
# "123^23456" to generate huge output 

#interface to "bc" calculator 
my $pid = open3(\*WRITE, \*READ,\*ERROR,"bc");
            #if \*ERROR is false, STDERR is sent to STDOUT  

while(1){

my($error,$answer,$rsize,$esize,$errortot,$answertot)=('','',0,0,'',''
+);

print "Enter expression for bc, i.e. 2 + 2\n";
chomp(my $query = <STDIN>);
if(length($query) == 0){next} #removes empty input 

#send query to bc 
print WRITE "$query\n";

#this do loop waits and eliminates need for a delay to let bc output 
#It is NOT limited to 4060 bytes from bc, it keeps reading 
#until a semi-full buffer is sent, which signals end of output 
  do {
      #see which filehandles have output from perldoc -q filehandle 
      $esize = pack("L", 0);
      ioctl(\*ERROR, FIONREAD(), $esize) or die "Couldn't call ioctl: 
+$!\n";
      $esize = unpack("L", $esize);
      print "esize-> $esize\n" unless ($esize < 1);

      $rsize = pack("L", 0);
      ioctl(\*READ, FIONREAD(), $rsize) or die "Couldn't call ioctl: $
+!\n";
      $rsize = unpack("L", $rsize);
      print "rsize-> $rsize\n" unless ($rsize <1);

     #get the output from bc 
     if($esize > 0){sysread(ERROR,$error,$esize); $errortot = $errorto
+t.$error}

#    needed this line on older linuxes and Perl, the pipes worked diff
+erent 
#     if($rsize > 0){sysread(READ,$answer,$rsize); $answertot = $answe
+rtot.$answer} 

# on newer kernels 2.6.x and Perl 5.8.7, this works 
     if($rsize > 0){sysread(READ,$answer,4096); $answertot = $answerto
+t.$answer}

  } until( ($esize > 0)  or ( ($rsize > 0) and ($rsize < 4096) )  );

if(length($errortot) > 0){ print "\e[1;31m ERROR-> $errortot \e[0m \n"
+}
if(length($answertot) > 0){print "Output->$query = $answertot\n" }

print OUT $answertot;
}

close OUT;

waitpid($pid, 1);
# It is important to waitpid on your child process,  
# otherwise zombies could be created.
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