use strict;
use warnings;
use feature "say";

sub hexgroups {
    my ( $n, $group ) = @_;

    die "Can't handle negative $n" if $n <0;

    $group //= 2;                       # default 1 byte = 2 nibbles

    my $nibbles = $n
      ? int( log($n)/log 16**$group ) +1
        : 1  ;                          # 00 has no log

    $nibbles *= $group;                 # zero padding

    my @list = sprintf( '%0*x', $nibbles, $n ) =~ /(.{$group})/g;

    return @list;
}



for my $n (0, map { 2*"1e$_"} 0..10) {
    say "$n => ";
    say "\t"x2, join " ",  hexgroups($n, $_) for 1,2,3,4;
}