Here is a classic case of why you should use strict; and use warnings; when you are writing Perl.

The first thing that jumps out at me is that Perl is not like C, a compiled language. Perl is an interpreted language and the use of my $y; is to establish the context of the variable not "define it" in the classical sense of the term. As long as you do not assign a value to $y it will have the psuedo-value of undef and hence the evaluation of the function defined($y) is going to return truefalse.

Just for tee-hees and ha-has I took your code and started playing around with it. First thing I did was add use strict; followed by use warnings;. All was happy util the  if ($y eq "") conditional whereupon the warning Use of uninitialized value in string eq at test.pl line 14 was issued.

OK... so let's initialize the variable. 

my $y = "";

[download]
Now the output becomes: 
Y is defined
Y is null string

[download]

Hope this helps.

updated:DOH! Saying true when I meant false....
Peter L. Berghold -- Unix Professional
Peter -at- Berghold -dot- Net; AOL IM redcowdawg Yahoo IM: blue_cowdawg

In reply to Re: defined vs null string by blue_cowdawg
in thread defined vs null string by Anonymous Monk

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