Do I need to use defined?

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

2017-10-07 Note added by Athanasius: This node was copied from StackOverflow. See also Re: Extract specify values in file log using perl.

Is there any difference between these 2:

print "Undefined\n" unless defined $test;

and

print "Undefined\n" unless $test;

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Re: Do I need to use defined? by hippo (Archbishop) on Sep 07, 2017 at 08:03 UTC
See also Checking Variable for Not Null where this was discussed previously.	[reply]
Re: Do I need to use defined? by Anonymous Monk on Sep 07, 2017 at 05:41 UTC
Yes. The second one will print when $test is 0, but the first one won't.	[reply]
Re^2: Do I need to use defined? by IruP (Initiate) on Sep 07, 2017 at 05:57 UTC
can you describe why?	[reply]
Re^3: Do I need to use defined? by roboticus (Chancellor) on Sep 07, 2017 at 06:02 UTC
Uh ... because 0 is defined. ...roboticus When your only tool is a hammer, all problems look like your thumb.	[reply]
Re^3: Do I need to use defined? by Anonymous Monk on Sep 07, 2017 at 06:19 UTC
In Perl, three things are false: the undefined value (`undef`), the empty string (`''`), and zero (`0`). Two of those things are `defined`.	[reply]
Re^4: Do I need to use defined? by afoken (Chancellor) on Sep 07, 2017 at 06:49 UTC
Re^5: Do I need to use defined? by Anonymous Monk on Sep 07, 2017 at 06:56 UTC
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