# Foo.pm package Foo; use strict; use warnings; use DateTime; sub new { my $class = shift; my $self = { _timevalue => DateTime->now, }; bless( $self, $class ); return $self; } # Modify _timevalue and return blessed reference sub _dumper_hook { $_[0] = bless { %{ $_[0] }, _timevalue => $_[0]->{_timevalue}->ymd . q{ } . $_[0]->{_timevalue}->hms, }, ref( $_[0] ); } 1; __END__