use File::Tail;

my $logfile = '/tmp/install.zsh.log';
my $child = open my $install_zsh, "| /bin/zsh $HOME/env/$ENV{DEST_SCRIPT_HOST}/db_silent_install/11gR2-11.2.0.1.0/install.zsh >$logfile";

# Sleep to give the logfile time to fill
sleep 5;

my $timeout = time + 60;

my $log = File::Tail->new($logfile);
while (defined($line=$log->read)) {
    print "$line";
    if( $line =~ /root user/ ) {
        print "Running magic helper commands as root\n";
        system("sudo ...") == 0 or die "$?";
        print "Sending ENTER to install script\n";
        print $child "\n";
    };
}