@success, @fail, @osuccess and @ofail messages may contain
%-substitutions, which evaluate to gender-specific pronouns if the
player's gender is set.

They are:
   %s (subjective) = Name, he, she, it
   %o (objective) = Name, him, her, it
   %p (possessive) = Name's, his, her, its
   %n (player's name) = Name.

If you want herself or himself or itself, use %oself.
If you want hers, use %ps.
 
Capitalized pronouns are also available with %S, %O, and %P.
If you need a '%', use %%.
Ex. '@ofail teapot=burns %p hand on the hot teapot.'

see also: gender, @osuccess, @ofail