# Change the base representation of a non-negative integer
use strict;
sub GenerateBase
{
    my $base = shift;
    $base = 62 if $base > 62;
    my @nums = (0..9,'a'..'z','A'..'Z')[0..$base-1];
    my $index = 0;
    my %nums = map {$_,$index++} @nums;

    my $To = sub
    {
        my $number = shift;
        return $nums[0] if $number == 0;
        my $rep = ""; # this will be the end value.
        while( $number > 0 )
        {
            $rep = $nums[$number % $base] . $rep;
            $number = int( $number / $base );
        }
        return $rep;
    };

    my $From = sub
    {
        my $rep = shift;
        my $number = 0;
        for( split //, $rep )
        {
            $number *= $base;
            $number += $nums{$_};
        }
        return $number;
    };

    return ( $To, $From );
}

=Example usage:

my( $ToBase62, $FromBase62 ) = GenerateBase( 62 );
my $UniqueID = $ToBase62->( $$ ) . $ToBase62->( time );

my $hex = (GenerateBase(16))[0];
print $hex->( '28' );

=cut