man > PERLFAQ9(1)

PERLFAQ9(1)                       Perl Programmers Reference Guide                       PERLFAQ9(1)

NAME
       perlfaq9 - Web, Email and Networking

VERSION
       version 5.20210520

DESCRIPTION
       This section deals with questions related to running web sites, sending and receiving email
       as well as general networking.

   Should I use a web framework?
       Yes. If you are building a web site with any level of interactivity (forms / users /
       databases), you will want to use a framework to make handling requests and responses easier.

       If there is no interactivity then you may still want to look at using something like Template
       Toolkit <https://metacpan.org/module/Template> or Plack::Middleware::TemplateToolkit so
       maintenance of your HTML files (and other assets) is easier.

   Which web framework should I use?
       There is no simple answer to this question. Perl frameworks can run everything from basic
       file servers and small scale intranets to massive multinational multilingual websites that
       are the core to international businesses.

       Below is a list of a few frameworks with comments which might help you in making a decision,
       depending on your specific requirements. Start by reading the docs, then ask questions on the
       relevant mailing list or IRC channel.

       Catalyst
           Strongly  object-oriented  and fully-featured with a long development history and a large
           community and addon ecosystem. It is excellent for large and complex applications,  where
           you have full control over the server.

       Dancer2
           Free  of  legacy  weight,  providing  a lightweight and easy to learn API.  Has a growing
           addon ecosystem. It is best used  for  smaller  projects  and  very  easy  to  learn  for
           beginners.

       Mojolicious
           Self-contained and powerful for both small and larger projects, with a focus on HTML5 and
           real-time web technologies such as WebSockets.

       Web::Simple
           Strongly  object-oriented  and  minimal,  built  for  speed and intended as a toolkit for
           building micro web apps,  custom  frameworks  or  for  tieing  together  existing  Plack-
           compatible web applications with one central dispatcher.

       All  of  these  interact  with  or  use Plack which is worth understanding the basics of when
       building   a   website   in   Perl   (there   is   a   lot   of   useful    Plack::Middleware
       <https://metacpan.org/search?q=plack%3A%3Amiddleware>).

   What is Plack and PSGI?
       PSGI  is the Perl Web Server Gateway Interface Specification, it is a standard that many Perl
       web frameworks use, you should not need to understand it to build a web site,  the  part  you
       might want to use is Plack.

       Plack   is   a   set   of   tools   for   using   the  PSGI  stack.  It  contains  middleware
       <https://metacpan.org/search?q=plack%3A%3Amiddleware>  components,  a  reference  server  and
       utilities  for  Web  application frameworks.  Plack is like Ruby's Rack or Python's Paste for
       WSGI.

       You could build a web site using Plack and your own code, but for anything other than a  very
       basic web site, using a web framework (that uses <https://plackperl.org>) is a better option.

   How do I remove HTML from a string?
       Use  HTML::Strip,  or  HTML::FormatText which not only removes HTML but also attempts to do a
       little simple formatting of the resulting plain text.

   How do I extract URLs?
       HTML::SimpleLinkExtor will extract URLs from  HTML,  it  handles  anchors,  images,  objects,
       frames,  and  many other tags that can contain a URL.  If you need anything more complex, you
       can create your  own  subclass  of  HTML::LinkExtor  or  HTML::Parser.  You  might  even  use
       HTML::SimpleLinkExtor as an example for something specifically suited to your needs.

       You can use URI::Find or URL::Search to extract URLs from an arbitrary text document.

   How do I fetch an HTML file?
       (contributed by brian d foy)

       The  core  HTTP::Tiny  module can fetch web resources and give their content back to you as a
       string:

           use HTTP::Tiny;

           my $ua = HTTP::Tiny->new;
           my $html = $ua->get( "http://www.example.com/index.html" )->{content};

       It can also store the resource directly in a file:

           $ua->mirror( "http://www.example.com/index.html", "foo.html" );

       If you need to do something more complicated, the HTTP::Tiny  object  can  be  customized  by
       setting  attributes,  or  you  can  use  LWP::UserAgent  from the libwww-perl distribution or
       Mojo::UserAgent from the Mojolicious distribution to make common tasks easier. If you want to
       simulate an interactive web browser, you can use the WWW::Mechanize module.

   How do I automate an HTML form submission?
       If you are doing something complex, such as moving through many pages  and  forms  or  a  web
       site, you can use WWW::Mechanize. See its documentation for all the details.

       If  you're submitting values using the GET method, create a URL and encode the form using the
       "www_form_urlencode" method from HTTP::Tiny:

           use HTTP::Tiny;

           my $ua = HTTP::Tiny->new;

           my $query = $ua->www_form_urlencode([ q => 'DB_File', lucky => 1 ]);
           my $url = "https://metacpan.org/search?$query";
           my $content = $ua->get($url)->{content};

       If  you're  using  the  POST  method,  the  "post_form"  method  will  encode   the   content
       appropriately.

           use HTTP::Tiny;

           my $ua = HTTP::Tiny->new;

           my $url = 'https://metacpan.org/search';
           my $form = [ q => 'DB_File', lucky => 1 ];
           my $content = $ua->post_form($url, $form)->{content};

   How do I decode or create those %-encodings on the web?
       Most of the time you should not need to do this as your web framework, or if you are making a
       request, the LWP or other module would handle it for you.

       To  encode  a  string yourself, use the URI::Escape module. The "uri_escape" function returns
       the escaped string:

           my $original = "Colon : Hash # Percent %";

           my $escaped = uri_escape( $original );

           print "$escaped\n"; # 'Colon%20%3A%20Hash%20%23%20Percent%20%25'

       To decode the string, use the "uri_unescape" function:

           my $unescaped = uri_unescape( $escaped );

           print $unescaped; # back to original

       Remember not to encode a full URI, you need to escape each component separately and then join
       them together.

   How do I redirect to another page?
       Most Perl Web Frameworks will have a mechanism for doing this, using the  Catalyst  framework
       it would be:

           $c->res->redirect($url);
           $c->detach();

       If  you  are using Plack (which most frameworks do), then Plack::Middleware::Rewrite is worth
       looking at if you are migrating from Apache or have URL's you want to always redirect.

   How do I put a password on my web pages?
       See if the web framework you are using has an authentication system and  if  that  fits  your
       needs.

       Alternativly look at Plack::Middleware::Auth::Basic, or one of the other Plack authentication
       <https://metacpan.org/search?q=plack+auth> options.

   How  do  I  make  sure  users  can't enter values into a form that causes my CGI script to do bad
       things?
       (contributed by brian d foy)

       You can't prevent people from sending your script bad data. Even if you add some  client-side
       checks,  people may disable them or bypass them completely. For instance, someone might use a
       module such as LWP to submit to your web site. If you want to prevent data that  try  to  use
       SQL  injection  or other sorts of attacks (and you should want to), you have to not trust any
       data that enter your program.

       The perlsec documentation has general advice about data security.  If you are using  the  DBI
       module,  use placeholder to fill in data.  If you are running external programs with "system"
       or "exec", use the list forms. There are many other precautions that  you  should  take,  too
       many  to  list  here, and most of them fall under the category of not using any data that you
       don't intend to use. Trust no one.

   How do I parse a mail header?
       Use the Email::MIME module. It's well-tested and supports all the craziness that  you'll  see
       in the real world (comment-folding whitespace, encodings, comments, etc.).

         use Email::MIME;

         my $message = Email::MIME->new($rfc2822);
         my $subject = $message->header('Subject');
         my $from    = $message->header('From');

       If you've already got some other kind of email object, consider passing it to Email::Abstract
       and then using its cast method to get an Email::MIME object:

         my $abstract = Email::Abstract->new($mail_message_object);
         my $email_mime_object = $abstract->cast('Email::MIME');

   How do I check a valid mail address?
       (partly contributed by Aaron Sherman)

       This isn't as simple a question as it sounds. There are two parts:

       a) How do I verify that an email address is correctly formatted?

       b) How do I verify that an email address targets a valid recipient?

       Without  sending  mail  to the address and seeing whether there's a human on the other end to
       answer you, you cannot fully answer part b, but the Email::Valid module will do both  part  a
       and part b as far as you can in real-time.

       Our  best  advice  for  verifying a person's mail address is to have them enter their address
       twice, just as you normally do to change a password. This usually weeds out  typos.  If  both
       versions  match,  send  mail  to that address with a personal message. If you get the message
       back and they've followed your directions, you can be reasonably assured that it's real.

       A related strategy that's less open to forgery is to give them a PIN  (personal  ID  number).
       Record  the  address and PIN (best that it be a random one) for later processing. In the mail
       you send, include a link to your site with the PIN included. If the mail  bounces,  you  know
       it's  not valid. If they don't click on the link, either they forged the address or (assuming
       they got the message) following through wasn't important so you don't need to worry about it.

   How do I decode a MIME/BASE64 string?
       The MIME::Base64 package handles this as well as the  MIME/QP  encoding.   Decoding  base  64
       becomes as simple as:

           use MIME::Base64;
           my $decoded = decode_base64($encoded);

       The  Email::MIME  module  can decode base 64-encoded email message parts transparently so the
       developer doesn't need to worry about it.

   How do I find the user's mail address?
       Ask them for it. There are so many email providers available that  it's  unlikely  the  local
       system has any idea how to determine a user's email address.

       The  exception is for organization-specific email (e.g. foo AT yourcompany.com) where policy can
       be codified in your program. In that case, you could look at $ENV{USER},  $ENV{LOGNAME},  and
       getpwuid($<) in scalar context, like so:

         my $user_name = getpwuid($<)

       But  you still cannot make assumptions about whether this is correct, unless your policy says
       it is. You really are best off asking the user.

   How do I send email?
       Use the Email::Stuffer module, like so:

         # first, create your message
         my $message = Email::Stuffer->from('you AT example.com')
                                     ->to('friend AT example.com')
                                     ->subject('Happy birthday!')
                                     ->text_body("Happy birthday to you!\n");

         $message->send_or_die;

       By default, Email::Sender::Simple (the "send" and "send_or_die" methods use  this  under  the
       hood)  will  try "sendmail" first, if it exists in your $PATH. This generally isn't the case.
       If there's a remote mail server you use to send  mail,  consider  investigating  one  of  the
       Transport classes. At time of writing, the available transports include:

       Email::Sender::Transport::Sendmail
           This is the default. If you can use the mail(1) or mailx(1) program to send mail from the
           machine where your code runs, you should be able to use this.

       Email::Sender::Transport::SMTP
           This  transport contacts a remote SMTP server over TCP. It optionally uses TLS or SSL and
           can authenticate to the server via SASL.

       Telling Email::Stuffer to use your transport is straightforward.

         $message->transport($email_sender_transport_object)->send_or_die;

   How do I use MIME to make an attachment to a mail message?
       Email::MIME directly supports multipart messages. Email::MIME objects  themselves  are  parts
       and  can  be attached to other Email::MIME objects. Consult the Email::MIME documentation for
       more information, including all of the supported methods and examples of their use.

       Email::Stuffer uses Email::MIME under the hood to construct  messages,  and  wraps  the  most
       common attachment tasks with the simple "attach" and "attach_file" methods.

         Email::Stuffer->to('friend AT example.com')
                       ->subject('The file')
                       ->attach_file('stuff.csv')
                       ->send_or_die;

   How do I read email?
       Use the Email::Folder module, like so:

         use Email::Folder;

         my $folder = Email::Folder->new('/path/to/email/folder');
         while(my $message = $folder->next_message) {
           # next_message returns Email::Simple objects, but we want
           # Email::MIME objects as they're more robust
           my $mime = Email::MIME->new($message->as_string);
         }

       There  are  different  classes  in the Email::Folder namespace for supporting various mailbox
       types. Note that these modules are generally rather limited and only support  reading  rather
       than writing.

   How do I find out my hostname, domainname, or IP address?
       (contributed by brian d foy)

       The Net::Domain module, which is part of the Standard Library starting in Perl 5.7.3, can get
       you the fully qualified domain name (FQDN), the host name, or the domain name.

           use Net::Domain qw(hostname hostfqdn hostdomain);

           my $host = hostfqdn();

       The Sys::Hostname module, part of the Standard Library, can also get the hostname:

           use Sys::Hostname;

           $host = hostname();

       The  Sys::Hostname::Long  module  takes  a  different approach and tries harder to return the
       fully qualified hostname:

         use Sys::Hostname::Long 'hostname_long';

         my $hostname = hostname_long();

       To get the IP address, you can use the "gethostbyname" built-in function  to  turn  the  name
       into  a  number.  To  turn  that number into the dotted octet form (a.b.c.d) that most people
       expect, use the "inet_ntoa" function from the Socket module, which also comes with perl.

           use Socket;

           my $address = inet_ntoa(
               scalar gethostbyname( $host || 'localhost' )
           );

   How do I fetch/put an (S)FTP file?
       Net::FTP, and Net::SFTP allow you to interact with FTP and SFTP (Secure FTP) servers.

   How can I do RPC in Perl?
       Use one of the RPC modules( <https://metacpan.org/search?q=RPC> ).

AUTHOR AND COPYRIGHT
       Copyright (c) 1997-2010 Tom Christiansen, Nathan Torkington, and other authors as noted.  All
       rights reserved.

       This  documentation is free; you can redistribute it and/or modify it under the same terms as
       Perl itself.

       Irrespective of its distribution, all code examples in this file are hereby placed  into  the
       public domain. You are permitted and encouraged to use this code in your own programs for fun
       or  for  profit as you see fit. A simple comment in the code giving credit would be courteous
       but is not required.

perl v5.38.2                                 2026-06-12                                  PERLFAQ9(1)