I have a short code for checking the sign of a permutation for personal use. It's O(L^2) where L is the length of the permutation vector, but it's perfectly fine for L in the few tens range.
function sign{T<:Integer}(perm::AbstractVector{T})
L = length(perm)
crosses = 0
for i = 1:L
for j = i+1 : L
crosses += perm[j] < perm[i]
end
end
return iseven(crosses) ? 1 : -1
end
