Heh.. this is great. One small bug fix needed though:

$ perl xp_o.pl 2731
XP = 2731
2731.00 initiates
136.55 novices, 11 to promotion
54.62 acolytes, 31 to promotion
27.31 scribes, 31 to promotion
13.65 monks, 131 to promotion
5.46 friars, 231 to promotion
2.73 abbots, 731 to promotion
1.71 bishops, 1131 to promotion
1.19 pontiffs, 431 to promotion
0.91 saints, 2731 to promotion
a pontiff, 2 monks, a novice, and 1a initiates
[download]

Note the "1a initiates". It should be 11. Replace the final bit with:

s<(?:^|\D)(1 [a-z]+(?:, 1 [a-z]+)*)>{
    my @ranks = $1 =~ /[a-z]+/g;
    " a " . join( ', ', @ranks )
}ge;
s/^ //;
if ( /,.+,/ ) {
    s/(.+),([^,]+)/$1, and$2/;
}
print
[download]

Which gives:

$ perl xp.pl 2731
XP = 2731
2731.00 initiates
136.55 novices, 11 to promotion
54.62 acolytes, 31 to promotion
27.31 scribes, 31 to promotion
13.65 monks, 131 to promotion
5.46 friars, 231 to promotion
2.73 abbots, 731 to promotion
1.71 bishops, 1131 to promotion
1.19 pontiffs, 431 to promotion
0.91 saints, 2731 to promotion
a pontiff, 2 monks, a novice, and 11 initiates
[download]