Invoking cdbdump from a bash script, hanging

Hi,

  I'm making a CDB database with really simple entries: an MD5 hash of
an email's body and a 0 or 1 if it is non-spam or spam.  A typical
transaction would be asking if an MD5 entry is in there.  A non-typical
one would be changing an entry's value from 0 to 1 or vice versa.
  I was going to use the Perl module CDB_File but it gets pretty slow
when you have 50k+ entries.
  Then I thought about using cdbdump as the database is pretty simple.
This works when I'm on the command line:
     cdbdump < data.cdb
      | sed 's/286466f8cabcfd520a78b337a5b69aa5->1/286466f8cabcfd520a78b337a5b69aa5->0/'
      | cdbmake data.cdb data.cdb.71952
  and is much faster than the Perl way.  So I through it into a script,
here's the meat of it:
     #!/bin/sh

     bindir="/usr/local/bin"
     DATA='data.cdb'

     command="$bindir/cdbdump < $DATA";
     echo "$command";
     `$command`;
  Running under strace you can see it hang waiting for STDIN.  I'm not
sure what's going wrong here.  The above works with cdbget so I know I'm
not crazy.
  Anyone use cdbdump in a shell script?  Is there a better way?

Chris