Why does string interpolation work in Ruby when there are no curly braces?

Why does string interpolation work in Ruby when there are no curly braces?

ruby string-interpolation

ruby

Use YAML with variables

ruby-on-rails ruby variables yaml string-interpolation

ruby

String concatenation vs. interpolation in Ruby

ruby string-concatenation string-interpolation

ruby

Does Python do variable interpolation similar to "string #{var}" in Ruby?

python ruby string-formatting string-interpolation language-comparisons

ruby

Rails String Interpolation in a string from a database

ruby string ruby-on-rails-3 string-interpolation

ruby

ruby 1.9 how to convert array to string without brackets

ruby arrays string version string-interpolation

ruby