use strict;
use warnings;
use IPC::Open2; 

my $cmd = 'C:\temp\abc.exe'; 
my $pid = open2(*RR,*WW,$cmd); 

print WW "5 \n";
print WW "iAmString \n";
print WW "\n"; # any key

while (<RR>) {
   chomp($_); 
   print "$_\n";
}
print "done \n";