Maybe I am missing something, but the only key you seem to use with the hash %dbase is "word". The string "word", not the contents of the $word variable. If all you want to do is to store the last processed word, it's not necessary to use a tied hash. Anyway if you do want to keep it and make sure the word does get stored in the file you have to flush it.

my $dbase_obj = tie (%dbase, 'DB_File', $dbase, O_CREAT|O_RDWR, 0644)
   || die "Died tying database\nReason: $!\n";
...

$dbase{word} = $word;
$dbase_obj->sync()
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Also please do NOT enclose variables in doublequotes, unless you do need to stringify a reference or something like that. "$variable" is almost always better written as $variable. If you are lucky, the doublequotes will just slow the script down, if not they will break it!

And there is another problem, the

  shift @words until $words[0] =~ m/$start/;
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looks for the first word that CONTAINS the last processed word. I don't think that's what you meant. I think you wanted this:

  shift @words until $words[0] eq $start;
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BTW, it's a shame some people don't agree with your sig. Well, to hell with some people! It's a shame my Squirrel thinks age does have some importance :-(