install_ifin my Gemfile to skip things not supported. I've recalled that
rubyslwas to be "already packaged and in the distribution".
bundle install, at least. Now, an actual incompatibility was what stops both rbx-3 and rbx-4. Someone was using Marshal.dump/Marshal.load.
for n ∈ 1:10 print(n) end
\in <Tab>and gets substituted
for n in 1:10 print(n) end
=in place of
for i in 1:m, j in 1:n B[i, j] = i + j end
C = [i + j for i in 1:m, j in 1:n]