mbethke,
Very nice. I had to slightly modify it in order to get the sort order I wanted: 
my @c3 = map { my $c = $_; (map { "$c$_" } @c1) } @c1;
sub myFromB37 {
    my $n = shift;
    my $s = '      ';
    substr( $s, 4, 2, $c3[$n % 1369] );
    $n /= 1369;
    substr( $s, 2, 2, $c3[$n % 1369] );
    $n /= 1369;
    substr( $s, 0, 2, $c3[$n] );
    $s;
}

my @c4;
$c4[unpack 'S', $c3[$_]] = $_ foreach 0 .. 1368;
sub myToB37 {
    1874161 * $c4[unpack 'S', substr($_[0], 0, 2)] +
       1369 * $c4[unpack 'S', substr($_[0], 2, 2)] +
              $c4[unpack 'S', substr($_[0], 4, 2)];
}

[download]
If you have time, I would really appreciate an in-depth explanation.

Cheers - L~R

In reply to Re^4: Fast - Compact That String by Limbic~Region
in thread Fast - Compact That String by Limbic~Region

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