How To Send Email With Perl, Part II
Part I contained an introduction and a working Perl script
for sending email. Part II assumes you understand the basic
concepts presented in Part I.
The script accompanying this part of the tutorial can send
text or HTML email, form user's choice or your choice. It
can be used as an auto-responder and can send personalized
emails. (Something to consider before sending HTML email
is that some email programs can't display HTML formatted
pages.)
The script is too large to be embedded within this article.
I'll be referring to it throughout. You can download it at
/library/demo/mailseries/part2.shtml
Please download the script before continuing. Without the
script to refer to, the rest of this article can be
confusing.
Unlike the basic script of Part I, this script uses Perl
module "strict" to enforce certain variable naming
conventions, which is good programming practice, and to
be usable on servers that run mod_perl. (mod_perl is an
Apache server module that speeds up Perl programs by a
considerable amount. Apache software is used by virtually
all Unix/Linux servers.)
Overview
First, the script checks whether or not an email address
was specified as part of the script's URL, in the manner
presented in Part I. If yes, the script stores the email
address where it can be referred to and used a bit later.
Then, in this order, the program:
-
Checks for and stores the values of any form fields
that might have been submitted to it.
-
Checks if any required form fields have been left
blank and whether or not the submitted address is
a valid email address, and displays error messages
as appropriate.
-
Sends the email, either plain text or HTML.
-
Displays the thankyou page in the user's browser.
Now, some details about each of the above four steps.
1. Form Field Values
The subroutine ParseValues is where the program checks for
and stores the values of form fields. It stores the values
in the %In hash variable, the key being the form field name
and the value being the form field value.
If a form is used to submit information to the program, the
method can be either POST or GET.
A form is not required for this program. An email address
can be submitted in the manner of the script in Part I.
2. Checking For Required Fields
If a form is used to submit information to the script,
it can have a hidden field name="required" with a value
containing the field name(s) that are required to have
information before the form can successfully be submitted.
If more than one form field name is required, separate them
with a comma. Example:
<input type="hidden" name="required"
value="firstname, email">
The subroutine CheckRequired ensures that all required form
fields contain information. The subroutine also uses another
subroutine, ValidEmail, to verify that the email address
stored in $In{email} is a validly formatted address. If
appropriate, subroutine CheckRequired presents an error
message to the user.
Subroutine WebPageErrorMessage is where error message web
pages are sent to the user's browser. You'll notice that
the last line of the subroutine is
goto BOTTOM;
That lines tells the script to jump to the label named
"BOTTOM" located near the bottom of the script. (The label
could be named anything you please. By convention, it is
all capital letters. I chose "BOTTOM" simply because it
is descriptive of where the label is located.)
The goto label method is used instead of the exit() function
so the script can run within mod_perl.
3. Sending the Email
The email is sent within subroutine SendEmail. It has a
number of useful features, each addressed below.
Email can be sent whether or not a form is used to submit
information to the script. For reference, a complete
example auto-responder's web page form is near the end
of this article.
Email Address --
If you use a form to submit information to the script,
there must be a form field name="email" that will contain
the email address where the email will be sent to. Example:
Email: <input type="text" name="email">
Type of Email --
As previously stated, the script can send plain text or
HTML email.
If a form is used to submit information to the script, you
can specify plain text or HTML email with a hidden, radio,
or checkbox name="html" field. To specify HTML, the value
is "yes". Otherwise, "no". Here is an example of each:
Hidden (to specify HTML):
<input type="hidden" name="html" value="yes">
Hidden (to specify plain text):
<input type="hidden" name="html" value="no">
Checkbox:
<input type="checkbox" name="html" value="yes">
Check for HTML email
Radio buttons:
<input type="radio" name="html" value="yes">HTML
<input type="radio" name="html" value="no">plain text
If no name="html" form field is present, plain text email
is assumed.
Personalization --
If you use a form to submit information to the script, the
information typed into the form fields can be used to
personalize the outgoing email.
When you specify the text of the outgoing email (see below),
use the form field name enclosed between double square
brackets to mark the place where that form field's contents
shall be inserted. Here is an example of such a placeholder:
[[firstname]]
The above placeholder will be replaced with the information
typed into a form field name="firstname", like:
First Name: <input type="text" name="firstname">
If no information exists to replace a placeholder with, the
placeholder will be removed before the email is sent.
Specifying and Formatting the Plain Text Email --
Put the plain text email between the lines containing the
characters: THE_PLAIN_EMAIL
You'll notice that the plain text email is formatted almost
exactly the same as the email in the script presented in
Part I of this tutorial. The differences are that the
placeholder [[email]] is used in the "To:" header line and
that additional placeholders may be used in the email body
content.
A placeholder may be used more than once in the same email.
Specifying and Formatting the HTML Email --
Put the HTML email between the lines containing the
characters: THE_HTML_EMAIL
Like the plain text email, the "To:" header line uses the
[[email]] placeholder.
You'll notice two additional header lines for HTML email:
Mime-Version: 1.0
Content-type: text/html; charset="iso-8859-1"
The email program that displays the email for the recipient
uses those lines to determine the type of email. If the
email program is capable of displaying HTML email, it will
do so.
The body content of the HTML email begins and ends with HEAD
and BODY tags, just like a regular web page. In between, you
can format the text as you please. You may use image tags.
You can create a form. In fact, you can do anything you
would with a regular web page, with two considerations:
-
All URLs in the body content must be complete
http://... URLs.
-
Some email programs are limited in the HTML tags
they recognize, which can cause the page to be
displayed differently than you had intended. If this
consideration is important to you, you may wish to
use only basic paragraph, header, and font tags
to format your HTML email.
Like the plain text email, HTML email may have placeholders
where specific form field information is to be inserted. A
placeholder may be used more than once in the same email.
4. The ThankYou Page
Once the email is sent, a "thank you" page is presented
to the user.
If a form is used to submit information to the script,
you can specify the thank you page with a hidden field
name="thankyoupage" and the URL of the thank you page
as the value. Example:
<input type="hidden" name="thankyoupage"
value="http://domain.com/thankyou.html">
If no thank you page URL is specified, a generic thank
you page is presented to the user.
Those were the four main subroutines the script uses to
process and respond to the information it receives.
An Example Auto-responder's Web Page Form
<form method="POST" action="/cgi-bin/part2.cgi">
<input type="hidden" name="thankyoupage"
value="http://domain.com/thankyou.html">
<input type="hidden" name="required"
value="firstname, email">
First Name:
<input type="text" name="firstname">
<br>
Email:
<input type="text" name="email">
<br>
<input type="radio" name="html" value="yes">HTML
<input type="radio" name="html" value="no">plain text
<br>
<input type="submit">
</form>
Still To Come
Still to come in this tutorial:
Obtaining the email content from a file instead of
embedded in the script. (You'll be able to change
the emails without modifying the script.)
The ability to send both text and HTML formatting
in the same email, so those with HTML email readers
see the HTML content and those with plain text
readers see the plain text content.
The ability to send email with one or more
attachments.
The ability receive and process email sent to an
email address like subscribe@domain.com
Watch for additional installments.
Will Bontrager
©2002 Bontrager Connection, LLC
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