How do I compare two objects in Perl without coercing them to the same type?

Question

In Perl, I know of three ways to test objects for equality: ==, eq, and ~~. All of these tell me that 1 is equal to "1" in Perl 5.

However, 1 and "1" are not the same thing. How can I compare two objects so that 1 equals 1, "1" equals "1", 1 does not equal "1" or 2, and "1" does not equal "01"? Answers for both Perls would be appreciated.

Answer 1

Don't. In Perl, one is one. Polymorphism based on a value's type is bound to fail. That's why Perl has two comparison operators, and that's why ~~ is broken^[1].

For example, the scalar returned by !0 contains three values, one stored as an integer, one stored as a floating point number, and one stored as a string.

For example, an object of class package Foo; use overload '0+' => sub { 1 }, fallback => 1; might not contain one at all, but it's considered to be one in numerical and string contexts.

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1. That's why it's still flagged as experimental.

Answer 2

Serializers like Data::Dumper::Dumper and JSON::encode_json can treat scalars internally stored as numbers differently from scalars internally stored as strings, so you can compare serialized output:

use Data::Dumper;
$x = 1;
$y = "1";
$same = Dumper($x) eq Dumper($y);