For example, $time->mon returns the month number (1-12) while $time->m
+onth returns the abbreviated name of the month.
Less is more:
$t->mon # 1 = January
$t->_mon # 0 = January
$t->monname # Feb
$t->month # same as $t->monname
$t->fullmonth # February
I much prefer the above documentation over renaming mon() and month() to month_number_starting_with_January_at_index_zero() and abbreviated_month_name(), or verbose 'explanations' cluttering up the place. Perhaps day_of_week() could say "same as $t->_wday()", but it seems pretty obvious to me that that is the case.
I infer from your response that, as far as you know, the answer to the question I asked is that there is not an explanation of Time::Piece::_wday in the module's documentation.
You infer incorrectly. IMHO, the amount of explanation already given is sufficient, and very little, if anything, should be added.