I'm writing a test harness. I want to correctly distinguish a scalar containing a number from a scalar containing a string.

Here is a simple program:

my $a = 3.0;
my $b = '3.0';

my $stringCompareResult = $a eq $b?'true':'false';
my $numberCompareResult = $a == $b?'true':'false';
print ("\$stringCompareResult: $stringCompareResult\n");
print ("\$numberCompareResult: $numberCompareResult\n");

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The result is:

$stringCompareResult: false<br>
$numberCompareResult: true<br>

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Since the string compare result is different for numbers and strings, the test matters.

How can I write a general is_number routine that answers, in this case, truth for $a and falsity for $b?

I've tried Scalar::Util::looks_like_number and also the following:

sub is_numeric {
  ($_[0] & ~ $_[0]) eq "0";
}

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Neither is able to correctly distinguish these two results.

In reply to Testing For Numberness Vs Stringness by BrooklineTom

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