perl - Perl and Template Toolkit: object stringify in custom filter

Question

in my template(via Template Toolkit), I pass a DateTime object(from DBIx::Class and DBIx::Class::InflateColumn::DateTime). I can do obj.year and all other DateTime operations in my template. But the object gets stringified in my custom filter. I am basically calling [% user.last_visited_date | time_ago %] where time_ago is a custom filter basically looks like this:

sub timeago { 
   sub { my $datetime_obj = shift; #do more work }
}

here I am expecting a DateTime obj in the custom filter but instead it is stringify..

How do I work around this?