$foo = $hash{5.00};

##</code><code>##

$foo = $hash{5};

##</code><code>##

$foo = $hash{'5.00'};

##</code><code>##

$hash{5} = "foo";
$hash{'5.00'} = "bar";
print $hash{5}, $hash{5.00}, $hash{'5.00'};