You could do the same by generating a closure to pass it $a == $self:

sub new { 
 my $self = {}; bless $self, $_[0];
 $self->{f} = sub { &foo ($self, @_); };
 return $self;
}
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The only reason for the three-line form with temporary variable is that I can't figure out how else to embed the closure "reference" to the object ($self) inside of an hash inside of the object itself :-)

(fixed minor typo!)