As an alternative to Expect, you could try IPC::Open3 (or IPC::Run or any of them), to run your script in an "expect like manner".

Check out the faq entry

8.25: How can I capture STDERR from an external command?
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You can also use the Searchbox and search for "IPC".

A super-simplified barebones example is below. IPC::OPen3 may not work in your particular case, and there can be many reasons why. In a real situation, you need to process the STDOUT and STDERR outputs with alot of regex's, then determine what reply to send to STDIN.

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

#interface to "bc" calculator 
#my $pid = open3(\*WRITE, \*READ, \*ERROR,"bc"); 
my $pid = open3(\*WRITE, \*READ,0,"bc");
            #if \*ERROR is false, STDERR is sent to STDOUT  

while(1){
print "Enter expression for bc, i.e. 2 + 2\n";
chomp(my $query = <STDIN>);

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

#give bc time to output 
select(undef,undef,undef,.5);

#get the answer from bc 
chomp(my $answer = <READ>);
print "$query = $answer\n";

}

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