package Foo; sub new { # A noop constructor bless {}, shift; } sub frobnicate { my($self, @args) = @_; unless($self eq 'Foo' || (ref $self && $self->isa('Foo'))) { unshift @args, $self; undef $self; } # Now $self is available only if you have an OO call # List of @args is always the same return join(', ', @args). "\n"; }