For explicit naming, you'll have to either use my blocks, or hash keys, or use constant. For efficiency and compactness, using constant names defined to indexes in an array is a good option for largish numbers of discrete values:

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

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

print "THIS:", $discrete[ THIS ];
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For multi-dim arrays, use subroutines:

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 );
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You could use nFor or Loops to write a generic multi-dim array reader, but unless you;re going above 3 or 4 dims, separate subs is probably easier. Watch the iteration order; it's can vary.

On my system, using a combination of :perlio on the open & binmode gives me the best reading speed. See Re^2: Perl's poor disk IO performance for details. YMMV.