Page 4: Use a Perl CGI script to validate your HTML forms.
This can make filling out the form tedious, and people might stop in the middle.
Let's build a simple form with a validation script.
I was recently asked how to implement time series cross-validation in R.
It checks to see if the required fields are there, and if not, saves an error message into a variable for display: The difference with how the CGI writes the error message is that instead of a "\n", it uses the HTML paragraph tag to put a new line in between each error.
Shows you how to write a script that ensures your form is filled in correctly before it's sent to your server.