For 2d:

use List::Util qw[ max maxstr ];

my @data2d = ...;

my $max = max( map max( @$_, ), @data2d );
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Or for multi-dimensional:

use List::Util qw[ max ];;

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

my @b = ...;;

print maxNd( @b );;
9981
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