use IPC::Open3;

local(*START_IN, *START_OUT, *START_ERR);

my $childpid = open3(*START_IN, *START_OUT, *START_ERR, 'external.sh');

while (<START_OUT>) {
        print;
        if (/Question1/) {
            print START_IN "Answer1";
        }
        elsif (/Question2/) {
            print START_IN "Answer2";
        }
}