Beefy Boxes and Bandwidth Generously Provided by pair Networks
good chemistry is complicated,
and a little bit messy -LW

Comment on

( #3333=superdoc: print w/ replies, xml ) Need Help??
We monks at the Monastery are glad to help. Those who seek knowledge can help themselves in their quest by following these guidelines, and asking these questions before posting:

Are you using the -w flag?

The "-w" command-line flag, or "use warnings;" in your code, turns on all sorts of warnings about probable errors. This will identify real problems much faster than we can. Plus, it's guaranteed that the first thing we'll ask is "Are you using the -w flag?"

Are you using use strict;?

"use strict" generates compile and run-time errors for certain unsafe variable, reference and subroutine constructs. The best part is that most of these problems are caused by simple typos. Guaranteed, it's the second thing we're going to ask.

Are you using use diagnostics;?

use diagnostics; causes warnings to be explained in greater detail. It can turn a cryptic message that only a monk could love into something that makes sense to one less experienced. This information is also in the perldiag page.

Describe the problem clearly

We need to know exactly what isn't working. "My script doesn't work" is not enough for us to work with. "Doesn't work" could mean anything from a syntax error, to showing incorrect data, to crashing the machine. For all we knew, your script made the server burst into flames. :-) (And if you DO write a script that manages to do that, please let us know about it!)
  • Do you get an error? What does the error say?
  • If it's a CGI script, what error is in the log file?
  • Do you get the wrong results? What results were you expecting, and what results did you actually get?

Tell us clearly what your program should do, and what it's actually doing. If we don't know how your program doesn't work, we can't fix it.

Describe what you've tried

Tell us what you've tried so that we don't suggest it again. Also, it can give us clues to pinpointing the problem. What have you tried to fix it that hasn't worked? What happened when you tried it?

Describe your environment

This gives us context and clues as to the causes. What version of Perl are you using? (Use perl -v to find out.) Are you on Windows? Unix? If you're doing a CGI script, what web server are you using? Do you have a firewall?

Have you checked the CPAN?

The CPAN is a vast collection of modules and other code that have been contributed and updated from other Perl programmers around the world.

For instance, if you're parsing CGI variables yourself, instead of using the CGI module, we're immediately going to say "Use the CGI module". Same thing for people who parse their own command-line arguments instead of using one of the GetOpt modules.

Use for your CGI scripts

Although it's possible to write your own code to handle CGI variables, cookies, etc, there's really no reason to not use Plus, there are a number of problems with using some other library and/or rolling your own. Lincoln Stein, the author of, has written Official Guide To Programming With that should never leave your side if you're writing CGI scripts. for reasons why you should be using see use CGI or die and no excuses for not using

Show the code

Please show whatever code you can. It's hard to diagnose the patient when the patient isn't in the doctor's office. And of course, use the <CODE> tags in your write-up so that it displays properly.

Show the data that goes with it

If you have a sample data set, provide it; If the set is too large, provide a sample piece of it. If most of the set works but a particular subset doesn't, provide a sample of what works and a sample of what does not.

If you think you don't have sample data, think again. For example, maybe your web-crawling robot chokes on a given URL. Tell us what that URL is.

Check common CGI problems

CGI scripts have their own set of challenges.

First, test it from the command line. I find that 99% of the time, scripts that don't run through the web browser are because of some sort of syntax errors that immediately show up when I run the script directly from the command line.

Second, use use CGI::Carp ':fatalsToBrowser'. This will catch your errors and send them to the browser, instead of the web server log.

Third, check The Idiot's Guide to Solving Perl CGI Problems. Tom's prose is unnecessarily combative, hostile and grating, but his points are still valid.

Write clearly

Use proper grammar, punctuation and spelling. Questions that are are hard to read don't get answered as often. Also, remember that for many Monks, English is not their first language, and may have trouble understanding you unless you follow the rules of English.

Is this even an appropriate question? is about learning about Perl. Questions about other languages or about general web issues are probably not appropriate.

And please don't ask us to do your homework assignments for you. There's no quicker way to draw the ire of a monk.

Other suggestions and additions will be incorporated over time.

Thanks to sifmole, Beatnik, LD2, tachyon and tilly for updates.


%_=split/;/,".;;n;u;e;ot;t;her;c; ".   #   Andy Lester
'Perl ;@; a;a;j;m;er;y;t;p;n;d;s;o;'.  #
"hack";print map delete$_{$_},split//,q<   >

In reply to How to get the most of your question from the monks by petdance

Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post; it's "PerlMonks-approved HTML":

  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • Outside of code tags, you may need to use entities for some characters:
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.
  • Log In?

    What's my password?
    Create A New User
    and the web crawler heard nothing...

    How do I use this? | Other CB clients
    Other Users?
    Others exploiting the Monastery: (9)
    As of 2014-07-13 16:53 GMT
    Find Nodes?
      Voting Booth?

      When choosing user names for websites, I prefer to use:

      Results (250 votes), past polls