In Ternary operator, a person wanting to join ["foo", "bar", "baz"] with commas and an "and" cited The Ruby Cookbook as saying
If efficiency is important to you, don't build a new string when you can append items onto an existing string. [And so on]... Use str << var1 << ' ' << var2 instead.
But the book was written in 2006.
Is using appending (ie <<) still the fastest way to build a large string given an array of smaller strings, in all major implementations of Ruby?