use constant {
    THIS => 0, THAT => 1, THEOTHER => 2, ...
    TEMPL1 => 'N A10 S',
};

my @discrete = unpack TEMPL1, read( $file, $size );

print "THIS:", $discrete[ THIS ];

##</code><code>##

sub get2DArray {
    my( $x, $y, $templ, $templSize, $fh ) = @_;
    my @array;
    for my $y ( 0 .. $y - 1 ) {
        push @array, [ unpack $templ . $x, read( $fh, $templSize * $x ) ];
    }
    return \@array;
}

my $array2D = get2DArray( 100, 100, 'N', 4, $fh );