package My::HTTPRequest ;
use base qw/HTTP::Request/ ;

sub new{
   my ($class) = shift ;
   my $self = $class->SUPER::new(@_) ;
   $self->{'myA'} = undef ;
   return bless $self, $class ;
}

sub myM{
  my ($self) = @_ ;
  ...
}

...

1;