#!/usr/bin/perl
use warnings;
use strict;
use IPC::Open3;

#interface to "units" calculator
my $pid = open3(\*WRITE, \*READ, 0 , "units -t");  # terse mode
            #if \*ERROR is set to 0, STDERR is sent to STDOUT 

foreach ( '100 yards', '1 mile', '1 kilometer', '1 parsec', '1 foobar'){  

print WRITE "$_\n meters \n";

chomp(my $answer = <READ>);
print "$_ = $answer meters\n";

}

__END__