I think the difference that confuses you is that some numbers can be represented by floating points without any error, while others can't. For example 0.1 is an infinite fraction in the binary system.

So while you can safely compare 0.5 * 2.0 == 1.0, you can't safely compare 0.1 * 2.0 == 0.2 (the former is true, the latter false).

The correct way to compare floating point numbers is 

if (abs($x-$y) < $epsilon) {...}

[download]

Where $epsilon is a small number.

Perl 6 - links to (nearly) everything that is Perl 6.

In reply to Re: eq vs == by moritz
in thread eq vs == by spikeheap

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