I think in Perl 5 this is platform specific, so I'll rather give the Perl 6 answer: 
my $num = Inf;
given $num {
    say "+Inf" when Inf;
    say "-Inf" when -Inf;
    say "NaN"  when NaN;
}

[download]

Works in Rakudo today.

In reply to Re: How do I create/detect/handle Infinity? by moritz
in thread How do I create/detect/handle Infinity? by jdporter

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