Data::Dumper(::Simple) is your friend

[cajun]

For a long time on PM I have seen people saying "use Data::Dumper" and look at your data. When I have seen this, I've always wondered why do I need to use a module to look at my data when it is so easy to print the data without a module.

foreach (@array){
  print "$_\n";
}

foreach (sort keys %hash){
  print "$_         $hash{$_}\n";
}

For the past couple of days I have been working on a piece of code that I just could NOT figure out why I was getting "Use of uninitialized value....". I used the snippet above several times. I wrote short scripts to prove to myself my code was working. Yet, in the actual script, the same code would not work.

My hash looked something like this:

1111   Fred
2222   Wilma
3333   Barney
4444   Betty

I struggled with this for a couple of days trying to see what was going on. Why was I getting this mysterious 'undef'. I thought about using Data::Dumper as I had seen so many times here. But I didn't get around to it until today.

I put in Data::Dumper::Simple and within 2 minutes saw the issue. My data that I thought looked like the above, really looked more like this:

'1111 ' -> 'Fred'
'2222 ' -> 'Wilma'
'3333 ' -> 'Barney'
'4444 ' -> 'Betty'

There was a trailing space in my keys. I would probably have never located this problem without Data::Dumper.

Data::Dumper(::Simple) is my new friend

I guess lessons learned the hard way are the ones you remember most easily.

M

Update: Thanks itub and Nkuvu. Both very good points. Using delimiters around the variables is an excellent idea that I will remember. Thanks.