my $remote_file="remote_file";
my $openstring="/usr/bin/rexec $host -l $user cat $remote_file |";
# note the cat command, and the pipe at the end
open FILE, $remote_file or die "Blerch: $!\n";
$md5=Digest::MD5->new();
while (<FILE>) {
  $md5->add($_);
}
close FILE;
print $md5->b64digest;
warn "Code is untested.";