X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=pod%2Fperlfaq9.pod;h=2649372cc6b409d61b25b7130ef669af31427362;hb=8269e00da02a2e0f107fbb8b4a78f0c4058f3587;hp=deeb6508ef9d8bcc4a5e66a446696077ef79a628;hpb=5a964f204835a8014f4ba86fc91884cff958ac67;p=p5sagit%2Fp5-mst-13.2.git

diff --git a/pod/perlfaq9.pod b/pod/perlfaq9.pod
index deeb650..2649372 100644
--- a/pod/perlfaq9.pod
+++ b/pod/perlfaq9.pod
@@ -1,43 +1,116 @@
 =head1 NAME
 
-perlfaq9 - Networking ($Revision: 1.17 $, $Date: 1997/04/24 22:44:29 $)
+perlfaq9 - Networking ($Revision: 1.26 $, $Date: 2005/11/21 17:43:13 $)
 
 =head1 DESCRIPTION
 
 This section deals with questions related to networking, the internet,
 and a few on the web.
 
-=head2 My CGI script runs from the command line but not the browser.  Can you help me fix it?
+=head2 What is the correct form of response from a CGI script?
 
-Sure, but you probably can't afford our contracting rates :-)
+(Alan Flavell <flavell+www@a5.ph.gla.ac.uk> answers...)
 
-Seriously, if you can demonstrate that you've read the following FAQs
-and that your problem isn't something simple that can be easily
-answered, you'll probably receive a courteous and useful reply to your
-question if you post it on comp.infosystems.www.authoring.cgi (if it's
-something to do with HTTP, HTML, or the CGI protocols).  Questions that
-appear to be Perl questions but are really CGI ones that are posted to
-comp.lang.perl.misc may not be so well received.
+The Common Gateway Interface (CGI) specifies a software interface between
+a program ("CGI script") and a web server (HTTPD). It is not specific
+to Perl, and has its own FAQs and tutorials, and usenet group,
+comp.infosystems.www.authoring.cgi
 
-The useful FAQs are:
+The CGI specification is outlined in an informational RFC:
+http://www.ietf.org/rfc/rfc3875
 
-    http://www.perl.com/perl/faq/idiots-guide.html
-    http://www3.pair.com/webthing/docs/cgi/faqs/cgifaq.shtml
-    http://www.perl.com/perl/faq/perl-cgi-faq.html
-    http://www-genome.wi.mit.edu/WWW/faqs/www-security-faq.html
-    http://www.boutell.com/faq/
+Other relevant documentation listed in: http://www.perl.org/CGI_MetaFAQ.html
+
+These Perl FAQs very selectively cover some CGI issues. However, Perl
+programmers are strongly advised to use the CGI.pm module, to take care
+of the details for them.
+
+The similarity between CGI response headers (defined in the CGI
+specification) and HTTP response headers (defined in the HTTP
+specification, RFC2616) is intentional, but can sometimes be confusing.
+
+The CGI specification defines two kinds of script: the "Parsed Header"
+script, and the "Non Parsed Header" (NPH) script. Check your server
+documentation to see what it supports. "Parsed Header" scripts are
+simpler in various respects. The CGI specification allows any of the
+usual newline representations in the CGI response (it's the server's
+job to create an accurate HTTP response based on it). So "\n" written in
+text mode is technically correct, and recommended. NPH scripts are more
+tricky: they must put out a complete and accurate set of HTTP
+transaction response headers; the HTTP specification calls for records
+to be terminated with carriage-return and line-feed, i.e ASCII \015\012
+written in binary mode.
+
+Using CGI.pm gives excellent platform independence, including EBCDIC
+systems. CGI.pm selects an appropriate newline representation
+($CGI::CRLF) and sets binmode as appropriate.
+
+=head2 My CGI script runs from the command line but not the browser.  (500 Server Error)
+
+Several things could be wrong.  You can go through the "Troubleshooting
+Perl CGI scripts" guide at
+
+	http://www.perl.org/troubleshooting_CGI.html
+
+If, after that, you can demonstrate that you've read the FAQs and that
+your problem isn't something simple that can be easily answered, you'll
+probably receive a courteous and useful reply to your question if you
+post it on comp.infosystems.www.authoring.cgi (if it's something to do
+with HTTP or the CGI protocols).  Questions that appear to be Perl
+questions but are really CGI ones that are posted to comp.lang.perl.misc
+are not so well received.
+
+The useful FAQs, related documents, and troubleshooting guides are
+listed in the CGI Meta FAQ:
+
+	http://www.perl.org/CGI_MetaFAQ.html
+
+
+=head2 How can I get better error messages from a CGI program?
+
+Use the CGI::Carp module.  It replaces C<warn> and C<die>, plus the
+normal Carp modules C<carp>, C<croak>, and C<confess> functions with
+more verbose and safer versions.  It still sends them to the normal
+server error log.
+
+    use CGI::Carp;
+    warn "This is a complaint";
+    die "But this one is serious";
+
+The following use of CGI::Carp also redirects errors to a file of your choice,
+placed in a BEGIN block to catch compile-time warnings as well:
+
+    BEGIN {
+        use CGI::Carp qw(carpout);
+        open(LOG, ">>/var/local/cgi-logs/mycgi-log")
+            or die "Unable to append to mycgi-log: $!\n";
+        carpout(*LOG);
+    }
+
+You can even arrange for fatal errors to go back to the client browser,
+which is nice for your own debugging, but might confuse the end user.
+
+    use CGI::Carp qw(fatalsToBrowser);
+    die "Bad error here";
+
+Even if the error happens before you get the HTTP header out, the module
+will try to take care of this to avoid the dreaded server 500 errors.
+Normal warnings still go out to the server error log (or wherever
+you've sent them with C<carpout>) with the application name and date
+stamp prepended.
 
 =head2 How do I remove HTML from a string?
 
-The most correct way (albeit not the fastest) is to use HTML::Parse
-from CPAN (part of the libwww-perl distribution, which is a must-have
-module for all web hackers).
+The most correct way (albeit not the fastest) is to use HTML::Parser
+from CPAN.  Another mostly correct
+way is to use HTML::FormatText which not only removes HTML but also
+attempts to do a little simple formatting of the resulting plain text.
 
 Many folks attempt a simple-minded regular expression approach, like
-C<s/E<lt>.*?E<gt>//g>, but that fails in many cases because the tags
+C<< s/<.*?>//g >>, but that fails in many cases because the tags
 may continue over line breaks, they may contain quoted angle-brackets,
-or HTML comment may be present.  Plus folks forget to convert
-entities, like C<&lt;> for example.
+or HTML comment may be present.  Plus, folks forget to convert
+entities--like C<&lt;> for example.
 
 Here's one "simple-minded" approach, that works for most files:
 
@@ -46,39 +119,76 @@ Here's one "simple-minded" approach, that works for most files:
 
 If you want a more complete solution, see the 3-stage striphtml
 program in
-http://www.perl.com/CPAN/authors/Tom_Christiansen/scripts/striphtml.gz
+http://www.cpan.org/authors/Tom_Christiansen/scripts/striphtml.gz
 .
 
+Here are some tricky cases that you should think about when picking
+a solution:
+
+    <IMG SRC = "foo.gif" ALT = "A > B">
+
+    <IMG SRC = "foo.gif"
+	 ALT = "A > B">
+
+    <!-- <A comment> -->
+
+    <script>if (a<b && a>c)</script>
+
+    <# Just data #>
+
+    <![INCLUDE CDATA [ >>>>>>>>>>>> ]]>
+
+If HTML comments include other tags, those solutions would also break
+on text like this:
+
+    <!-- This section commented out.
+        <B>You can't see me!</B>
+    -->
+
 =head2 How do I extract URLs?
 
-A quick but imperfect approach is
+You can easily extract all sorts of URLs from HTML with
+C<HTML::SimpleLinkExtor> which 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
+C<HTML::LinkExtor> or C<HTML::Parser>.  You might even use
+C<HTML::SimpleLinkExtor> as an example for something specifically
+suited to your needs.
+
+You can use URI::Find to extract URLs from an arbitrary text document.
+
+Less complete solutions involving regular expressions can save
+you a lot of processing time if you know that the input is simple.  One
+solution from Tom Christiansen runs 100 times faster than most
+module based approaches but only extracts URLs from anchors where the first
+attribute is HREF and there are no other attributes.
+
+        #!/usr/bin/perl -n00
+        # qxurl - tchrist@perl.com
+        print "$2\n" while m{
+            < \s*
+              A \s+ HREF \s* = \s* (["']) (.*?) \1
+            \s* >
+        }gsix;
 
-    #!/usr/bin/perl -n00
-    # qxurl - tchrist@perl.com
-    print "$2\n" while m{
-	< \s*
-	  A \s+ HREF \s* = \s* (["']) (.*?) \1
-	\s* >
-    }gsix;
-
-This version does not adjust relative URLs, understand alternate
-bases, deal with HTML comments, deal with HREF and NAME attributes in
-the same tag, or accept URLs themselves as arguments.  It also runs
-about 100x faster than a more "complete" solution using the LWP suite
-of modules, such as the
-http://www.perl.com/CPAN/authors/Tom_Christiansen/scripts/xurl.gz
-program.
 
 =head2 How do I download a file from the user's machine?  How do I open a file on another machine?
 
-In the context of an HTML form, you can use what's known as
-B<multipart/form-data> encoding.  The CGI.pm module (available from
-CPAN) supports this in the start_multipart_form() method, which isn't
-the same as the startform() method.
+In this case, download means to use the file upload feature of HTML
+forms.  You allow the web surfer to specify a file to send to your web
+server.  To you it looks like a download, and to the user it looks
+like an upload.  No matter what you call it, you do it with what's
+known as B<multipart/form-data> encoding.  The CGI.pm module (which
+comes with Perl as part of the Standard Library) supports this in the
+start_multipart_form() method, which isn't the same as the startform()
+method.
+
+See the section in the CGI.pm documentation on file uploads for code
+examples and details.
 
 =head2 How do I make a pop-up menu in HTML?
 
-Use the B<E<lt>SELECTE<gt>> and B<E<lt>OPTIONE<gt>> tags.  The CGI.pm
+Use the B<< <SELECT> >> and B<< <OPTION> >> tags.  The CGI.pm
 module (available from CPAN) supports this widget, as well as many
 others, including some that it cleverly synthesizes on its own.
 
@@ -90,16 +200,22 @@ on your system, is this:
     $html_code = `lynx -source $url`;
     $text_data = `lynx -dump $url`;
 
-The libwww-perl (LWP) modules from CPAN provide a more powerful way to
-do this.  They work through proxies, and don't require lynx:
+The libwww-perl (LWP) modules from CPAN provide a more powerful way
+to do this.  They don't require lynx, but like lynx, can still work
+through proxies:
 
-    # print HTML from a URL
+    # simplest version
     use LWP::Simple;
-    getprint "http://www.sn.no/libwww-perl/";
+    $content = get($URL);
 
-    # print ASCII from HTML from a URL
+    # or print HTML from a URL
     use LWP::Simple;
-    use HTML::Parse;
+    getprint "http://www.linpro.no/lwp/";
+
+    # or print ASCII from HTML from a URL
+    # also need HTML-Tree package from CPAN
+    use LWP::Simple;
+    use HTML::Parser;
     use HTML::FormatText;
     my ($html, $ascii);
     $html = get("http://www.perl.com/");
@@ -108,45 +224,104 @@ do this.  They work through proxies, and don't require lynx:
     $ascii = HTML::FormatText->new->format(parse_html($html));
     print $ascii;
 
-=head2 how do I decode or create those %-encodings on the web?
+=head2 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 C<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 C<query_form> method:
+
+    use LWP::Simple;
+    use URI::URL;
+
+    my $url = url('http://www.perl.com/cgi-bin/cpan_mod');
+    $url->query_form(module => 'DB_File', readme => 1);
+    $content = get($url);
+
+If you're using the POST method, create your own user agent and encode
+the content appropriately.
 
-Here's an example of decoding:
+    use HTTP::Request::Common qw(POST);
+    use LWP::UserAgent;
 
-    $string = "http://altavista.digital.com/cgi-bin/query?pg=q&what=news&fmt=.&q=%2Bcgi-bin+%2Bperl.exe";
-    $string =~ s/%([a-fA-F0-9]{2})/chr(hex($1))/ge;
+    $ua = LWP::UserAgent->new();
+    my $req = POST 'http://www.perl.com/cgi-bin/cpan_mod',
+                   [ module => 'DB_File', readme => 1 ];
+    $content = $ua->request($req)->as_string;
 
-Encoding is a bit harder, because you can't just blindly change
-all the non-alphanumunder character (C<\W>) into their hex escapes.
-It's important that characters with special meaning like C</> and C<?>
-I<not> be translated.  Probably the easiest way to get this right is
-to avoid reinventing the wheel and just use the URI::Escape module,
-which is part of the libwww-perl package (LWP) available from CPAN.
+=head2 How do I decode or create those %-encodings on the web?
+
+If you are writing a CGI script, you should be using the CGI.pm module
+that comes with perl, or some other equivalent module.  The CGI module
+automatically decodes queries for you, and provides an escape()
+function to handle encoding.
+
+The best source of detailed information on URI encoding is RFC 2396.
+Basically, the following substitutions do it:
+
+    s/([^\w()'*~!.-])/sprintf '%%%02x', ord $1/eg;   # encode
+
+    s/%([A-Fa-f\d]{2})/chr hex $1/eg;                # decode
+	s/%([[:xdigit:]]{2})/chr hex $1/eg;          # same thing
+
+However, you should only apply them to individual URI components, not
+the entire URI, otherwise you'll lose information and generally mess
+things up.  If that didn't explain it, don't worry.  Just go read
+section 2 of the RFC, it's probably the best explanation there is.
+
+RFC 2396 also contains a lot of other useful information, including a
+regexp for breaking any arbitrary URI into components (Appendix B).
 
 =head2 How do I redirect to another page?
 
-Instead of sending back a C<Content-Type> as the headers of your
-reply, send back a C<Location:> header.  Officially this should be a
-C<URI:> header, so the CGI.pm module (available from CPAN) sends back
-both:
+Specify the complete URL of the destination (even if it is on the same
+server). This is one of the two different kinds of CGI "Location:"
+responses which are defined in the CGI specification for a Parsed Headers
+script. The other kind (an absolute URLpath) is resolved internally to
+the server without any HTTP redirection. The CGI specifications do not
+allow relative URLs in either case.
+
+Use of CGI.pm is strongly recommended.  This example shows redirection
+with a complete URL. This redirection is handled by the web browser.
+
+      use CGI qw/:standard/;
+
+      my $url = 'http://www.cpan.org/';
+      print redirect($url);
+
+
+This example shows a redirection with an absolute URLpath.  This
+redirection is handled by the local web server.
 
-    Location: http://www.domain.com/newpage
-    URI: http://www.domain.com/newpage
+      my $url = '/CPAN/index.html';
+      print redirect($url);
+
+
+But if coded directly, it could be as follows (the final "\n" is
+shown separately, for clarity), using either a complete URL or
+an absolute URLpath.
+
+      print "Location: $url\n";   # CGI response header
+      print "\n";                 # end of headers
 
-Note that relative URLs in these headers can cause strange effects
-because of "optimizations" that servers do.
 
 =head2 How do I put a password on my web pages?
 
-That depends.  You'll need to read the documentation for your web
-server, or perhaps check some of the other FAQs referenced above.
+To enable authentication for your web server, you need to configure
+your web server.  The configuration is different for different sorts
+of web servers---apache does it differently from iPlanet which does
+it differently from IIS.  Check your web server documentation for
+the details for your particular server.
 
 =head2 How do I edit my .htpasswd and .htgroup files with Perl?
 
 The HTTPD::UserAdmin and HTTPD::GroupAdmin modules provide a
 consistent OO interface to these files, regardless of how they're
-stored.  Databases may be text, dbm, Berkley DB or any database with a
-DBI compatible driver.  HTTPD::UserAdmin supports files used by the
-`Basic' and `Digest' authentication schemes.  Here's an example:
+stored.  Databases may be text, dbm, Berkeley DB or any database with
+a DBI compatible driver.  HTTPD::UserAdmin supports files used by the
+"Basic" and "Digest" authentication schemes.  Here's an example:
 
     use HTTPD::UserAdmin ();
     HTTPD::UserAdmin
@@ -155,21 +330,14 @@ DBI compatible driver.  HTTPD::UserAdmin supports files used by the
 
 =head2 How do I make sure users can't enter values into a form that cause my CGI script to do bad things?
 
-Read the CGI security FAQ, at
-http://www-genome.wi.mit.edu/WWW/faqs/www-security-faq.html, and the
-Perl/CGI FAQ at
-http://www.perl.com/CPAN/doc/FAQs/cgi/perl-cgi-faq.html.
+See the security references listed in the CGI Meta FAQ
 
-In brief: use tainting (see L<perlsec>), which makes sure that data
-from outside your script (eg, CGI parameters) are never used in
-C<eval> or C<system> calls.  In addition to tainting, never use the
-single-argument form of system() or exec().  Instead, supply the
-command and arguments as a list, which prevents shell globbing.
+	http://www.perl.org/CGI_MetaFAQ.html
 
 =head2 How do I parse a mail header?
 
 For a quick-and-dirty solution, try this solution derived
-from page 222 of the 2nd edition of "Programming Perl":
+from L<perlfunc/split>:
 
     $/ = '';
     $header = <MSG>;
@@ -182,54 +350,112 @@ the Mail::Header module from CPAN (part of the MailTools package).
 
 =head2 How do I decode a CGI form?
 
-A lot of people are tempted to code this up themselves, so you've
-probably all seen a lot of code involving C<$ENV{CONTENT_LENGTH}> and
-C<$ENV{QUERY_STRING}>.  It's true that this can work, but there are
-also a lot of versions of this floating around that are quite simply
-broken!
+(contributed by brian d foy)
+
+Use the CGI.pm module that comes with Perl.  It's quick,
+it's easy, and it actually does quite a bit of work to
+ensure things happen correctly.  It handles GET, POST, and
+HEAD requests, multipart forms, multivalued fields, query
+string and message body combinations, and many other things
+you probably don't want to think about.
+
+It doesn't get much easier: the CGI module automatically
+parses the input and makes each value available through the
+C<param()> function.
+
+	use CGI qw(:standard);
+
+	my $total = param( 'price' ) + param( 'shipping' );
+
+	my @items = param( 'item' ); # multiple values, same field name
+
+If you want an object-oriented approach, CGI.pm can do that too.
+
+	use CGI;
 
-Please do not be tempted to reinvent the wheel.  Instead, use the
-CGI.pm or CGI_Lite.pm (available from CPAN), or if you're trapped in
-the module-free land of perl1 .. perl4, you might look into cgi-lib.pl
-(available from http://www.bio.cam.ac.uk/web/form.html).
+	my $cgi = CGI->new();
+
+	my $total = $cgi->param( 'price' ) + $cgi->param( 'shipping' );
+
+	my @items = $cgi->param( 'item' );
+
+You might also try CGI::Minimal which is a lightweight version
+of the same thing.  Other CGI::* modules on CPAN might work better
+for you, too.
+
+Many people try to write their own decoder (or copy one from
+another program) and then run into one of the many "gotchas"
+of the task.  It's much easier and less hassle to use CGI.pm.
 
 =head2 How do I check a valid mail address?
 
-You can't.
-
-Without sending mail to the address and seeing whether it bounces (and
-even then you face the halting problem), you cannot determine whether
-an mail address is valid.  Even if you apply the mail header
-standard, you can have problems, because there are deliverable
-addresses that aren't RFC-822 (the mail header standard) compliant,
-and addresses that aren't deliverable which are compliant.
-
-Many are tempted to try to eliminate many frequently-invalid mail
-addresses with a simple regexp, such as
-C</^[\w.-]+\@([\w.-]\.)+\w+$/>.  However, this also throws out many
-valid ones, and says nothing about potential deliverability, so is not
-suggested.  Instead, see
-http://www.perl.com/CPAN/authors/Tom_Christiansen/scripts/ckaddr.gz ,
+You can't, at least, not in real time.  Bummer, eh?
+
+Without sending mail to the address and seeing whether there's a human
+on the other end to answer you, you cannot determine whether a mail
+address is valid.  Even if you apply the mail header standard, you
+can have problems, because there are deliverable addresses that aren't
+RFC-822 (the mail header standard) compliant, and addresses that aren't
+deliverable which are compliant.
+
+You can use the Email::Valid or RFC::RFC822::Address which check
+the format of the address, although they cannot actually tell you
+if it is a deliverable address (i.e. that mail to the address
+will not bounce).  Modules like Mail::CheckUser and Mail::EXPN
+try to interact with the domain name system or particular
+mail servers to learn even more, but their methods do not
+work everywhere---especially for security conscious administrators.
+
+Many are tempted to try to eliminate many frequently-invalid
+mail addresses with a simple regex, such as
+C</^[\w.-]+\@(?:[\w-]+\.)+\w+$/>.  It's a very bad idea.  However,
+this also throws out many valid ones, and says nothing about
+potential deliverability, so it is not suggested.  Instead, see
+http://www.cpan.org/authors/Tom_Christiansen/scripts/ckaddr.gz ,
 which actually checks against the full RFC spec (except for nested
 comments), looks for addresses you may not wish to accept mail to
 (say, Bill Clinton or your postmaster), and then makes sure that the
-hostname given can be looked up in DNS.  It's not fast, but it works.
+hostname given can be looked up in the DNS MX records.  It's not fast,
+but it works for what it tries to do.
+
+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 that looks somewhat like:
 
-Here's an alternative strategy used by many CGI script authors: Check
-the mail address with a simple regexp (such as the one above).  If
-the regexp matched the address, accept the address.  If the regexp
-didn't match the address, request confirmation from the user that the
-mail address they entered was correct.
+    Dear someuser@host.com,
+
+    Please confirm the mail address you gave us Wed May  6 09:38:41
+    MDT 1998 by replying to this message.  Include the string
+    "Rumpelstiltskin" in that reply, but spelled in reverse; that is,
+    start with "Nik...".  Once this is done, your confirmed address will
+    be entered into our records.
+
+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, ask them to
+include the PIN in their reply.  But if it bounces, or the message is
+included via a "vacation" script, it'll be there anyway.  So it's
+best to ask them to mail back a slight alteration of the PIN, such as
+with the characters reversed, one added or subtracted to each digit, etc.
 
 =head2 How do I decode a MIME/BASE64 string?
 
-The MIME-tools package (available from CPAN) handles this and a lot
-more.  Decoding BASE64 becomes as simple as:
+The MIME-Base64 package (available from CPAN) handles this as well as
+the MIME/QP encoding.  Decoding BASE64 becomes as simple as:
 
-    use MIME::base64;
+    use MIME::Base64;
     $decoded = decode_base64($encoded);
 
-A more direct approach is to use the unpack() function's "u"
+The MIME-Tools package (available from CPAN) supports extraction with
+decoding of BASE64 encoded attachments and content directly from email
+messages.
+
+If the string to decode is short (less than 84 bytes long)
+a more direct approach is to use the unpack() function's "u"
 format after minor transliterations:
 
     tr#A-Za-z0-9+/##cd;                   # remove non-base64 chars
@@ -239,12 +465,12 @@ format after minor transliterations:
 
 =head2 How do I return the user's mail address?
 
-On systems that support getpwuid, the $E<lt> variable and the
+On systems that support getpwuid, the $< variable, and the
 Sys::Hostname module (which is part of the standard perl distribution),
 you can probably try using something like this:
 
     use Sys::Hostname;
-    $address = sprintf('%s@%s', getpwuid($<), hostname);
+    $address = sprintf('%s@%s', scalar getpwuid($<), hostname);
 
 Company policies on mail address can mean that this generates addresses
 that the company's mail system will not accept, so you should ask for
@@ -257,58 +483,154 @@ It makes a more intelligent guess than the code above, using information
 given when the module was installed, but it could still be incorrect.
 Again, the best way is often just to ask the user.
 
-=head2 How do I send/read mail?
-
-Sending mail: the Mail::Mailer module from CPAN (part of the MailTools
-package) is UNIX-centric, while Mail::Internet uses Net::SMTP which is
-not UNIX-centric.  Reading mail: use the Mail::Folder module from CPAN
-(part of the MailFolder package) or the Mail::Internet module from
-CPAN (also part of the MailTools package).
-
-   # sending mail
-    use Mail::Internet;
-    use Mail::Header;
-    # say which mail host to use
-    $ENV{SMTPHOSTS} = 'mail.frii.com';
-    # create headers
-    $header = new Mail::Header;
-    $header->add('From', 'gnat@frii.com');
-    $header->add('Subject', 'Testing');
-    $header->add('To', 'gnat@frii.com');
-    # create body
-    $body = 'This is a test, ignore';
-    # create mail object
-    $mail = new Mail::Internet(undef, Header => $header, Body => \[$body]);
-    # send it
-    $mail->smtpsend or die;
-
-=head2 How do I find out my hostname/domainname/IP address?
-
-A lot of code has historically cavalierly called the C<`hostname`>
-program.  While sometimes expedient, this isn't very portable.  It's
-one of those tradeoffs of convenience versus portability.
-
-The Sys::Hostname module (part of the standard perl distribution) will
-give you the hostname after which you can find out the IP address
-(assuming you have working DNS) with a gethostbyname() call.
+=head2 How do I send mail?
+
+Use the C<sendmail> program directly:
+
+    open(SENDMAIL, "|/usr/lib/sendmail -oi -t -odq")
+                        or die "Can't fork for sendmail: $!\n";
+    print SENDMAIL <<"EOF";
+    From: User Originating Mail <me\@host>
+    To: Final Destination <you\@otherhost>
+    Subject: A relevant subject line
+
+    Body of the message goes here after the blank line
+    in as many lines as you like.
+    EOF
+    close(SENDMAIL)     or warn "sendmail didn't close nicely";
+
+The B<-oi> option prevents sendmail from interpreting a line consisting
+of a single dot as "end of message".  The B<-t> option says to use the
+headers to decide who to send the message to, and B<-odq> says to put
+the message into the queue.  This last option means your message won't
+be immediately delivered, so leave it out if you want immediate
+delivery.
+
+Alternate, less convenient approaches include calling mail (sometimes
+called mailx) directly or simply opening up port 25 have having an
+intimate conversation between just you and the remote SMTP daemon,
+probably sendmail.
+
+Or you might be able use the CPAN module Mail::Mailer:
+
+    use Mail::Mailer;
+
+    $mailer = Mail::Mailer->new();
+    $mailer->open({ From    => $from_address,
+                    To      => $to_address,
+                    Subject => $subject,
+                  })
+        or die "Can't open: $!\n";
+    print $mailer $body;
+    $mailer->close();
+
+The Mail::Internet module uses Net::SMTP which is less Unix-centric than
+Mail::Mailer, but less reliable.  Avoid raw SMTP commands.  There
+are many reasons to use a mail transport agent like sendmail.  These
+include queuing, MX records, and security.
+
+=head2 How do I use MIME to make an attachment to a mail message?
+
+This answer is extracted directly from the MIME::Lite documentation.
+Create a multipart message (i.e., one with attachments).
+
+    use MIME::Lite;
+
+    ### Create a new multipart message:
+    $msg = MIME::Lite->new(
+                 From    =>'me@myhost.com',
+                 To      =>'you@yourhost.com',
+                 Cc      =>'some@other.com, some@more.com',
+                 Subject =>'A message with 2 parts...',
+                 Type    =>'multipart/mixed'
+                 );
+
+    ### Add parts (each "attach" has same arguments as "new"):
+    $msg->attach(Type     =>'TEXT',
+                 Data     =>"Here's the GIF file you wanted"
+                 );
+    $msg->attach(Type     =>'image/gif',
+                 Path     =>'aaa000123.gif',
+                 Filename =>'logo.gif'
+                 );
+
+    $text = $msg->as_string;
+
+MIME::Lite also includes a method for sending these things.
+
+    $msg->send;
+
+This defaults to using L<sendmail> but can be customized to use
+SMTP via L<Net::SMTP>.
+
+=head2 How do I read mail?
+
+While you could use the Mail::Folder module from CPAN (part of the
+MailFolder package) or the Mail::Internet module from CPAN (part
+of the MailTools package), often a module is overkill.  Here's a
+mail sorter.
+
+    #!/usr/bin/perl
+
+    my(@msgs, @sub);
+    my $msgno = -1;
+    $/ = '';                    # paragraph reads
+    while (<>) {
+        if (/^From /m) {
+            /^Subject:\s*(?:Re:\s*)*(.*)/mi;
+            $sub[++$msgno] = lc($1) || '';
+        }
+        $msgs[$msgno] .= $_;
+    }
+    for my $i (sort { $sub[$a] cmp $sub[$b] || $a <=> $b } (0 .. $#msgs)) {
+        print $msgs[$i];
+    }
+
+Or more succinctly,
 
-    use Socket;
-    use Sys::Hostname;
-    my $host = hostname();
-    my $addr = inet_ntoa(scalar(gethostbyname($name)) || 'localhost');
+    #!/usr/bin/perl -n00
+    # bysub2 - awkish sort-by-subject
+    BEGIN { $msgno = -1 }
+    $sub[++$msgno] = (/^Subject:\s*(?:Re:\s*)*(.*)/mi)[0] if /^From/m;
+    $msg[$msgno] .= $_;
+    END { print @msg[ sort { $sub[$a] cmp $sub[$b] || $a <=> $b } (0 .. $#msg) ] }
+
+=head2 How do I find out my hostname, domainname, or IP address?
+X<hostname, domainname, IP address, host, domain, hostfqdn, inet_ntoa,
+gethostbyname, Socket, Net::Domain, Sys::Hostname>
+
+(contributed by brian d foy)
+
+The Net::Domain module, which is part of the standard distribution starting
+in perl5.7.3, can get you the fully qualified domain name (FQDN), the host
+name, or the domain name.
 
-Probably the simplest way to learn your DNS domain name is to grok
-it out of /etc/resolv.conf, at least under Unix.  Of course, this
-assumes several things about your resolv.conf configuration, including
-that it exists.
+	use Net::Domain qw(hostname hostfqdn hostdomain);
+	
+	my $host = hostfqdn();
 
-(We still need a good DNS domain name-learning method for non-Unix
-systems.)
+The C<Sys::Hostname> module, included in the standard distribution since
+perl5.6, can also get the hostname.
+
+	use Sys::Hostname;
+	
+	$host = hostname();
+
+To get the IP address, you can use the C<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 C<inet_ntoa> function
+from the <Socket> module, which also comes with perl.
+
+    use Socket;
+    
+    my $address = inet_ntoa( 
+    	scalar gethostbyname( $host || 'localhost' )
+    	);
 
 =head2 How do I fetch a news article or the active newsgroups?
 
 Use the Net::NNTP or News::NNTPClient modules, both available from CPAN.
-This can make tasks like fetching the newsgroup list as simple as:
+This can make tasks like fetching the newsgroup list as simple as
 
     perl -MNews::NNTPClient
       -e 'print News::NNTPClient->new->list("newsgroups")'
@@ -320,21 +642,18 @@ available from CPAN) is more complex but can put as well as fetch.
 
 =head2 How can I do RPC in Perl?
 
-A DCE::RPC module is being developed (but is not yet available), and
-will be released as part of the DCE-Perl package (available from
-CPAN).  No ONC::RPC module is known.
+(Contributed by brian d foy)
+
+Use one of the RPC modules you can find on CPAN (
+http://search.cpan.org/search?query=RPC&mode=all ).
 
 =head1 AUTHOR AND COPYRIGHT
 
-Copyright (c) 1997, 1998 Tom Christiansen and Nathan Torkington.
-All rights reserved.
+Copyright (c) 1997-2005 Tom Christiansen, Nathan Torkington, and
+other authors as noted. All rights reserved.
 
-When included as part of the Standard Version of Perl, or as part of
-its complete documentation whether printed or otherwise, this work
-may be distributed only under the terms of Perl's Artistic License.
-Any distribution of this file or derivatives thereof I<outside>
-of that package require that special arrangements be made with
-copyright holder.
+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