Return to the previous form

I'm working through Learn Python The Hard Way, and I'm currently working on Exercise 51, which asks the student to add a back link in the templates / index.html file so we can continue filling out the form and see the results. My code looks like this:

/bin
    app.py
/static
/templates
    hello_form.html
    index.html
/tests

      

        
        
        
      

    

app.py is written like this:

import web

urls = (
    '/hello', 'Index'
    )

app = web.application(urls, globals())

render = web.template.render('templates/', base="layout")

class Index(object):
    def GET(self):
        return render.hello_form()

    def POST(self):
        form = web.input(name="Nobody", greet="Hello")
        greeting = "%s, %s" % (form.greet, form.name)
        return render.index(greeting = greeting)

if __name__ == "__main__":
    app.run()

      

        
        
        
      

    

index.html written like this:

$def with (greeting)

$if greeting:
    I just wanted to say <em style="color: green; font-size: 2em;">$greeting</em>
$else:
    <em>Hello</em>, world!

      

        
        
        
      

    

hello_form.html is written like this:

<h1>Fill out this form</h1>

<form action="/hello" method="POST">
    A Greeting: <input type="text" name="greet">
    <br/>
    Your Name: <input type="text" name="name">
    <br/>
    <input type="submit">
</form>

      

        
        
        
      

    

This link is a button on a form, isn't it? How do I add a handler for this button?

Thanks in advance for your help.