The problem is that parsersettings.check is being called twice--parsersettings.execute calls it, as does dbcparse.rb
(line 137).  This has the effect of overwriting the string data read from STDIN into @source in parsersettings.rb. 
Commenting out line 137 of dbcparse.rb fixes the problem:

###    settings.check
    settings.execute

Date: 2005-08-05 20:42
Sender: Charles Mills

Thanks for reporting this... I have been away from DBC for a
while.  I apply fix.

-Charlie