- sprintf "%3.1f%1s", $_[0] / 1000 ** $unit,
- $#{$opt{units}} >> 1 < abs $unit ? "e$unit" : $opt{units}->[$unit];
+ my $float = $_[0] !~ /^ (?: 0*\.)? [0-9]{1,3} $/x;
+ sprintf('%*.*f%*s',
+ $float ? 5 : 3, $float, # length and tenths
+ $_[0] / 1000 ** $unit, # number
+ $float ? 1 : 3, # unit size
+ $#{$opt{units}} >> 1 < abs $unit ? "e$unit" : $opt{units}->[$unit]
+ );