f = chain(function $f(it) { return `a:${it}` })
g = chain(function $g(it) { return `b:${it}` })

fg1 = chain(f)(g) // this works as expected
fg2 = chain(chain(f)(g)) // this gives a bound wrapper
fg3 = chain(fg1) // this gives undefined.

// the outputs are generated by running fg('c')