use List::Util qw[ max maxstr ];

my @data2d = ...;

my $max = max( map max( @$_, ), @data2d ); 

##</code><code>##

use List::Util qw[ max ];;

sub maxNd { max( map{ ref() ? maxNd( @$_ ) : $_  } @_ ) };;

my @b = ...;;

print maxNd( @b );;
9981