my @c1 = (' ', '0'..'9', 'A'..'Z' );
sub fromB37 {
    my $n = shift;
    my $s = '      ';
    substr( $s, $_, 1, $c1[ $n%37 ] ), $n /= 37 for 5, 4, 3, 2, 1, 0;
    $s;
}

my @c2;
$c2[  ord( $c1[ $_ ] ) ] = $_ for 0 .. 36;
sub toB37 {
    my $n = 0;
    $n = $n * 37 + $c2[$_] for unpack 'C*', $_[0];
    $n;
}