Re^2: "defined" function fails to evaluate expression; feature or fault?

Not that it makes any difference in this case, but defined returns '' (the empty string; false) or 1 (true):

c:\@Work\Perl>perl -wMstrict -le
"print 'perl version ', $];
 ;;
 print 'undefined A: >', defined(),      '<';
 print 'undefined B: >', defined(undef), '<';
 print 'defined: >',     defined(42),    '<';
"
perl version 5.008009
undefined A: ><
undefined B: ><
defined: >1<

perl version 5.014004
undefined A: ><
undefined B: ><
defined: >1<
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Give a man a fish: <%-{-{-{-<

Comment on Re^2: "defined" function fails to evaluate expression; feature or fault? Select or Download Code

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Re^3: "defined" function fails to evaluate expression; feature or fault? by haukex (Archbishop) on Jan 27, 2017 at 07:44 UTC
Hi AnomalousMonk, defined returns `''` (the empty string; false) or `1` (true) To be even more specific, Perl has a "special" value for "false" - see Truth and Falsehood. The difference between an empty string and the special "false" value: `$ perl -wMstrict -le 'my $x=""; print 3+$x;' Argument "" isn't numeric in addition (+) at -e line 1. 3 $ perl -wMstrict -le 'my $x=!!""; print 3+$x;' 3 $ perl -wMstrict -le 'my $x=defined(); print 3+$x;' 3` [download] And looking even more closely with Devel::Peek: Read more... (862 Bytes) Regards, -- Hauke D Update 2019-08-17: Updated the link to "Truth and Falsehood".	[reply] [d/l] [select]
Re^3: "defined" function fails to evaluate expression; feature or fault? by stevieb (Canon) on Jan 26, 2017 at 21:13 UTC
Yep, I caught that after doing some testing, and had updated my reply (at least I thought I fixed it all). Thanks for the heads-up, as if someone is expecting a zero and is getting the empty-string type false instead, it could cause head-scratching.	[reply]