http://prezi.com/csbyxwomcsoi/more-wtf-in-perl-yapceu2010-pisa/

See also:

1. YAPC EU 2010 is coming
2. My presentation at YAPC::EU::2009 was graded
3. WTFish side of using Perl talk at YAPC::EU 2009 – slides

Turn AdBlock off and look at right column. First, there are ads about perl – form Gabor – I wrote about it here. Then a few adsense (from Google). They should match the content of this blog. And then is a link to one particular book I like very much.

And guess what? No one clicks the ads from Google. I see that in my stats. Even though those ads are matched to site content – as you can see. I doubt if anyone clicks the ads from Gabor either (by analogy – beside, I guess, most geeks use adblock and similar solutions – so they do not even see it – and those ads are intended for THEM). If you have clicked and ad here – either from Gabors perl ad server, or google – raise your hand (add a comment).

See also:

1. Advertise Perl with Gabor
2. Microsoft bots made DDoS on CPAN
3. Utf8 in web perl application (LAMP) – binmode, charset

See http://jquelin.blogspot.com/2010/02/ironman-challenge-status.html and http://www.lowlevelmanager.com/2010/01/perl-iron-man-challenge-is-cron-still.html

wtf?

See also:

1. WTFish side of using Perl talk at YAPC::EU 2009 – slides
2. YAPC::EU 2010 Pisa – my presentation
3. More on foreach localisation

I was honoured to meet Larry Wall, who told me to have “appropiate amount of fun” on my presentation about WTFs.

A few minutes earlier I met Damian Conway, whom I helped with aplying last-minute changes to conference schedule and putting in on conference room door, before I realised who he was.

Paul Fenwick dressed as Star Trek hero did presentation about klingon Perl programming. A bit earlier this day, Damian Conway did completely different presentation about klingon Perl programming, making with his voice sounds that soon made him thirsty.

to be continued…

See also:

1. Nice people I met at YAPC::EU – continued
2. YAPC EU 2010 is coming
3. My presentation at YAPC::EU::2009 was graded

After the conference attendees are encouraged to express their opinions on presentations they attended and grade them. Then the aggregated grades and opinions are sent to speaker.

I was a bit nervous, but fortunately presentation about WTFish side of using Perl was graded between 7 and 10 (on a scale from 1 to 10), mostly 8-9.

There were also opinions – good and bad.

Bad: I could have been speaking louder and with better intonation and gestures. Slides also could be a bit better. Someone even wrote “Poor guy, it is hard to present in another language. I hope he isnt disheartened, his presentation is good”

Good opinions (quoted from the feedback I got):

• Covered well some common but not obvious traps in Perl for newbies. The material was good.
• Good title and subject – humourous way to present this sid of Perl. As a total beginner some parts I knew of and felt the same WTFness and it is nice to feel that it is as mad as I thought!
• This presentation pin pointed some of the things that regularly “bite” newbies, so it was most valuable. It had many examples, and I hope I can remember them all. [ note: there are slides available to download at this blog, so you don't have to remeber all   - Lech ]

Poor guy, it is hard to present in another language.	I hope he isnt
  disheartened, his presentation is good

Thanks for good opinions and also for bad – those taught me something about presentations. Next time it will be better

See also:

1. WTFish side of using Perl talk at YAPC::EU 2009 – slides
2. YAPC::EU 2010 Pisa – my presentation
3. YAPC::EU 2009 in Lisboa (Lisbon, Lizbona)!

Nice:

• bug-fixes, optimisations, tuning. Runs faster.
• autodie pragma

Strange:

• “..” operator is interpretedin boolean context when used inside a when statement – yet another WTF. So, the behaviour of “..” is not less consistent. On the other hand it may be usefull.
• Change of smart match behavior in comaprison to 5.10
1. better encapsulation
2. ordering matters – $key ~~ %hash is OK, while %hash ~~ $key is not.
3. distributive – applies itself recursively across data structures.  Isn’t it getting too smart? And too complex to understand in real code? And too WTFish? I’ll quote the fragment of perl tips newsletter from http://perltraining.com.au/
   

   following expression is *true* when evaluated under 5.10.1, but *false*
   under 5.10.0:

   ‘bar’ ~~ [ 'foo', [ 'bar', 'baz' ], ‘qux’ ]

   In the same vein, given the following code:

   [ 'foo', 'bar', 'baz' ] ~~ \&subroutine

   Perl 5.10.1 will call the subroutine *three* times (once for each
   element), and the whole expression will be considered true if *all* the
   results are true. On the other hand, Perl 5.10.0 would call the
   subroutine only once, passing in the whole data structure.

See also:

1. More on foreach localisation
2. Utf8 in web perl application (LAMP) – part 2 – Encode
3. Utf8 in web perl application (LAMP)

One day I was using global var in script (lame, I know). I wanted to use it in foreach. And its value magically disappeared when called other subroutine. This was strange.

This was a script to make reports for customers. The code looked like this (many parts taken out for brevity and to protect the innocent ) :


#!/usr/bin/perl
use strict;
use warnings;
my $custid; # to store customerid.
my %rep_conf;
$rep_conf{'Something-GmBH'}{'custid'}=12345;
(...more config data kept in that hash...)
my $cust_name; # customer name
foreach $cust_name (keys %rep_conf) { # in that hash we get report configuration. The key was customer name.
print("$cust_name"); # here is still exists
$custid = $rep_conf{$cust_name}{'custid'}; # customer id was taken from config hash
$firstsheet = &get_sheet; # get data for our report
(...)
sub get_sheet {
print($custid); # works
print($cust_name); # empty. WTF?
(...)


I scratched my head – why the $custid value exists and $cust_name value disappeared?

I had I hunch to read about foreach in perl docs:

The foreach loop iterates over a normal list value and sets the variable VAR to be each element of the list in turn. If the variable is preceded with the keyword my, then it is lexically scoped, and is therefore visible only within the loop.

Sounds rational. But it was no “my” there:
foreach $cust_name (keys %rep_conf)

Otherwise, the variable is implicitly local to the loop and regains its former value upon exiting the loop.
If the variable was previously declared with my, it uses that variable instead of the global one, but it’s still localized to the loop. This implicit localisation occurs only in a foreach loop.

Here is the mystery solved.  Strange indeed – only for/foreach loop behaves like this.

See also:

1. Perl 5.10.1
2. Perl WTFs – last in function
3. Utf8 in web perl application (LAMP) – part 2 – Encode

• http://perl.baczynski.com/lisboa/WTF.odt
• http://perl.baczynski.com/lisboa/WTF.pdf

Feedback about my talk is appreciated, use comment field below

See also:

1. My presentation at YAPC::EU::2009 was graded
2. YAPC::EU 2009 in Lisboa (Lisbon, Lizbona)!
3. Nice people I met at YAPC::EU

for … {

something…;

function();

something… that would not be executed…

};

sub function {

something something…

last; # by mistake, maybe it should be a “return”?

}

For some people it is a WTF, for some it is very logical way , that it should work like.

What do you think about it?

See also:

1. WTFish side of using Perl talk at YAPC::EU 2009 – slides
2. More on foreach localisation
3. Perl 5.10.1