In the new program -dmerge, that is now available from the SSC archives, I categorized the program as a "modification" of Stata's -merge-. This was imprecise terminology. -dmerge- is a wrapper around Stata's merge rather than a modification of the command. The wrapper adds some features and alters some of -merge-'s printed output.
Fred Wolfe
*
*   For searches and help try:
*   http://www.stata.com/support/faqs/res/findit.html
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/