erb_lvars.rb

require 'erb'

module TemplateVariables
  def self.construct(variables)
    b = get_binding
    variables.each do |key, value|
      b.local_variable_set(key, value)
    end

    b
  end

  def self.get_binding
    binding
  end
end

h = {entity: "World", greeting: "Hello"}
b = TemplateVariables.construct(h)
ERB.new("<%= greeting %> <%= entity %>!").result b
# => "Hello World!"