use Digest::MD5;

my $host = "host";
my $remote_file = "remote_file";

    my $remote_file = "/usr/bin/rexec $host -l $user $remote_file";
    open(FILE, $remote_file) or die "Can't open '$remote_file': $!";
    binmode(FILE);

    $md5 = Digest::MD5->new;
    while (<FILE>) {
        $md5->add($_);
    }
    close(FILE);
    print $md5->b64digest, " $remote_file\n";