Definine a procedure named "combine" causes map to fail mysteriously

[PammyBA]

For example, this combine will cause BH's subsets to give bizarre output:

to combine :list1 :list2
if emptyp :list1 [output :list2]
output fput first :list1 combine butfirst :list1 :list2
end

to subsets :word
if emptyp :word [output (sentence ")]
local "smaller
make "smaller subsets butfirst :word
output sentence :smaller (map [word (first :word) ?] :smaller)
end

I gather there is a 'combine' library procedure, which I discovered after much pondering. This took me an hour to solve, so perhaps a warning or something when a library is redefined?

[brianharvey]

Yeah, we need a package system, or something.