I'm using Stata 14.2 and was trying to use the duplicates command, when I experienced some strange behaviour and I haven't found a similar case on the forum. If I put a hyphen in a varlist, the duplicates tag works perfectly, but the duplicates drop returns an error saying - invalid name. If I have many variables to be considered, it's burdensome to list them all. Is it the same in later versions?

Edit: The force was missing from the end of the command, so it works well, just the error message is slightly misleading.

Code:
input a b c
1 1 1
1 1 1
2 1 1
end
duplicates tag a - c, generate(d)
duplicates drop a - c