class CGI

Since Ruby 4.0, CGI is a small holder for various escaping methods, included from CGI::Escape

require 'cgi/escape'

CGI.escape("Ruby programming language")
#=> "Ruby+programming+language"
CGI.escapeURIComponent("Ruby programming language")
#=> "Ruby%20programming%20language"

See CGI::Escape module for methods list and their description.