Changing data frame column headings

I have a reshaped data frame with value column headings concatenated from
two column headings in the melted data frame. I want to change all 56
headings in a single command, but 'names' allows me to change only one at a
time. In Hadley's 2007 article on reshape in the Journal of Statistical
Software he mentions a 'rename' function, but I cannot find that.

   Is there a way to change all data frame column headings in a single
command?

Rich