I was just meditating last night, and thought about your problem. I had a thought( better duck :-) ). If the RSPerl is an interpreter, which you send commands to stdin and get results out of stdout, you probably should run it thru IPC::Open3. I have sample code below

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

$|=1;

#my $pid=open3(\*IN,\*OUT,\*ERR,'/bin/bash');
my $pid=open3(\*IN,\*OUT,0,'/bin/bash');
# set \*ERR to 0 to send STDERR to STDOUT
my $cmd = 'date';
#my $cmd = 'top';
#send cmd to bash
print IN "$cmd\n";

#getresult
my $result = <OUT>;
print $result;
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Now you should be able to do a similar thing with the RSPerl interpreter. Of course, in a real script, you may want to separate stdout and stderr, and use IO::Select. Search for examples of IPC::Open3 for more detailed usage.

Now, once you get IPC::Open3 to run the interpreter, you can put the code into a thread, and pass in strings to be eval'd thru ther shared variable mechanism.