define(f,`ifelse(`$1',,,`f(patsubst(``~$1'',~.*
))On the %s day of Christmas,
my true love sent to me
patsubst(`$1',\
A,\&nd a)
')')regexp(format((f(patsubst(``Twelve drummers drumm!Eleven pipers pip!Ten lords a-leap!Nine ladies danc!Eight maids a-milk!Seven swans a-swimm!Six geese a-lay!Five golden rings,
Four calling birds,
Three French hens,
Two turtle doves,
A partridge in a pear tree.
'',!,`ing,
'))),first,second,third,patsubst(four!fif!six!seven!eigh!nin!ten!eleven!twelf!,!,`th,')),O[^~]*e,\&!)