I'm not sure why you can't use Expect, but the other alternative is to use IPC, read perldoc perlipc

Here is a super simple example using the bc calculator, but you would run your script. This uses IPC::Open2 which comes standard in Perl. Just plugin your script, and answer the prompts in order as you receive them.

#!/usr/bin/perl
#prompts for an string to evalute
#(line 2+2, or 5x7, 5*6 / 3 , etc)
#sends it to the bc calculator, 
#then reads the answer, and prints.
use IPC::Open2;
use strict;
use warnings;

my ($rd, $wr);
open2($rd, $wr, "bc");

print "Enter a string to evaluate\n";
my $prompt= <STDIN>;
print $wr "$prompt";
my $x = <$rd>;
print $x;


print "Enter another string to evaluate\n";
my $prompt= <STDIN>;
print $wr "$prompt";
my $x = <$rd>;
print $x;

close($rd);
close($wr);
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