#! perl -slw
use strict;
use Time::HiRes qw[ time ];

my @c = (' ', '0'..'9', 'A'..'Z' );
sub fromB37 {
    my $n = shift;
    join '', map {
        my $c = $n %37;
        $n = int( $n / 37 );
        $c[ $c ];
    } 1 .. 6;
}

my %c = map{ $c[ $_ ] => $_ } 0 .. 36;
sub toB37 {
    my $n = 0;
    $n = $n * 37 + $c{$_} for reverse unpack '(a)*', $_[0];
    return $n;
}

my $start = time;

for ( 1 .. 1e6 ) {
    my $n = int( rand 37**6 );
    $n == toB37( fromB37( $n ) ) or die $n;
}

printf "Took %.3f second\n", time() - $start;

__END__
C:\test>junk45
Took 16.404 second