How to try examples given in the documentation...

When I read through the online documentation, for example, for
"form_tag", I see a number of examples shown as:

  form_tag('/posts')
  # => <form action="/posts" method="post">

  form_tag('/posts/1', :method => :put)
  # => <form action="/posts/1" method="put">

  form_tag('/upload', :multipart => true)
  # => <form action="/upload" method="post" enctype="multipart/form-data">

  <% form_tag '/posts' do -%>
    <div><%= submit_tag 'Save' %></div>
  <% end -%>
  # => <form action="/posts" method="post"><div><input type="submit"
name="submit" value="Save" /></div></form>

Is it possible to try these examples at a command prompt somehow? I
tried starting up script/console and typing in

form_tag('/posts')

   hoping to get back out something like:
<form action="/posts" method="post">

But I got the very unintuitive error message:

NoMethodError: undefined method `form_tag' for #<Object:0x27bf9ec>
     from (irb):1

It was especially unintuitive when I tracked down "form_tag_helper.rb"
and saw in it ...

module ActionView
  module Helpers
    module FormTagHelper
      def form_tag(url_for_options = {}, options = {},
*parameters_for_url, &block) ...

So I tried ActionView::Helpers::FormTagHelper::form_tag(...) and got
the same error message. I am thinking that this has to do with Ruby's
notion of "sending a message via method" clashing with my notion of
"invoking a procedure".

Can anybody point me in the direction of how to poke and prod at the
various capabilities provided by Rails from a command prompt?

Thanks...

--wpd