In this case, though, I was trying to make certain that the non-backslash characters preceeding the variable did not get included in the match result.

As you pointed out below, though, the look-behind assertion was what I had in mind, but for some reason I was lead to believe that they didn't work properly in some cases, but those cases seem to be pretty specific, or related to some earlier version of perl. merlyn had provided a demonstration on the perils of negative lookback, but I can't find it.