Hi, just as a curiosity, to see if I could run units thru some form of IPC, I tried to run it with IPC::Open3. I had some trouble with it going into a runaway condition, until I added the -t (terse) switch. I also had trouble with getting the full output from the pipe after each prompt. But anyways, here is a running version.

#!/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__
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OUTPUT:

100 yards = 91.44 meters
1 mile = 1609.344 meters
1 kilometer = 1000 meters
1 parsec = 3.0856776e+16 meters
1 foobar = Unknown unit 'foobar' meters
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