My best solution is 47 characters:

#!/usr/local/bin/perl -l

print hole(uc $_) for @ARGV;

sub hole {
#        1         2         3         4
#2345678901234567890123456789012345678901234567
my$d;map$d=$d*36+(/\d/?$_:-55+ord),pop=~/./g;$d
}
[download]

The simple framework allows for convenient testing: % perl base36.pl 1 A 10