Perl encode/decoder of base62 format

base62.pl

use constant PRIMITIVES => join( '', 0 .. 9, 'a' .. 'z', 'A' .. 'Z' );

sub encode_base62 {
    my( $num ) = @_;
    my @c;
    do {
	      push( @c, substr( PRIMITIVES, $num % length(PRIMITIVES), 1 ) );
	      $num = int( $num / length(PRIMITIVES) );
    } while( $num );
    join( '', reverse @c );
}

sub decode_base62 {
    my( $str ) = @_;
    my $num = 0;
    my $place = 1;
    for my $c ( reverse split( //, $str ) ){
	      $num += index(PRIMITIVES, $c) * $place;
	      $place *= length(PRIMITIVES);
    }
    $num;
}