Sounds like an easy question, doesn't it? But let's make it a challenge. Write a subroutine, accepting a single argument, and using pure Perl only, return true if its argument is zero, false otherwise.

Here are a few arguments that should result in true being returned: 

$x = 0;
$x = "0";
$x = 0.0;
$x = Scalar::Util::dualvar 0, 1;

[download]
But it should return false on the following: 
$x = 1;
$x = "foo";
$x = "00";
$x = "0 ";
$x = undef;
$x = "";
$x = Scalar::Util::dualvar 1, 0;
$x = "0.0";

[download]

In reply to Determining whether a value is zero. by JavaFan

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