$num = '-0.0000009';
$num = sprintf("%7.5f",$num);
$num = $num == 0 ? '0.00000' : $num;
print "$num\n";

##</code><code>##

$num = sprintf("%7.5f",$num) || '0.00000';

##</code><code>##

$num = sprintf("%7.5f",$num)+0 || '0.00000';