http://www.perlmonks.org?node_id=773137

corenth has asked for the wisdom of the Perl Monks concerning the following question:

I am trying to parse a simple string. In doing so, I want to get rid of quotes. The regex as it stands doesn't reflect the possibility of escaped quotes.

Let's take this string: '1,2,3,4,"fine","day","today",'

If I could remove all the qoutes (or didn't care) I could use: 


@a = $string =~/

(  #capture matches and put them into @a
        (?:\d+) | (?:"(?:.+?)")

)
/gx;


print Dumper \@a;

[download]
to give me : 


$VAR1 = [
          '1',
          '2',
          '3',
          '4',
          '"fine"',
          '"day"',
          '"today"'
        ];

[download]
I don't wan't those quotes, so I : 

@b = $string =~/

(?:    #don't capture matches

        (\d+) | (?:"(.+?)")   

#capture numbers and anything inside of quotes


)
/gx;

print Dumper \@b;

[download]
which gives me: 
        
$VAR1 = [
          '1',
          undef,
          '2',
          undef,
          '3',
          undef,
          '4',
          undef,
          undef,
          'fine',
          undef,
          'day',
          undef,
          'today'
        ];

[download]
Oh NO!!! all those undefs and I might want to use a hash instead of an array!! Oh, what can I do? 


@c =


map {/.+/g}   #if it's an undef, it's NOT getting into that array ;)


$string =~/

(?:
        (\d+) | (?:"(.+?)")

)
/gx;

print Dumper \@c;

[download]
to get: 
$VAR1 = [
          '1',
          '2',
          '3',
          '4',
          'fine',
          'day',
          'today'
        ];

[download]
LOVELY!!

But why? Granted, this exercise has helped me to understand map() alot better, but I would like to know what it is about my pattern that creates all those undefs, and I would like to know how (if there's a way) I could do this without all those undefs.

I'm happy with my solution, but I'm unhappy with the fact that I don't understand the problem. If you have an idea about how to help me understand, I'd be very thankful.

---

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