There is, of course, the putrid and horrible, yet sublimely simple additive solution...

print "print an example of negative zero\n";
@range = (-0.0000001, -0.000001, -0.00001, -0.0001);

foreach $example (@range)
{
    $tret = sprintf("rounded float:%7.5f, other:%7.5e",$example+.00000
+4,$example);
    
    print "The Number $example is represented as $tret\n";
}
[download]

Update: .000004 not .0000009 actually seems to work