sub Y { my ( $curried_rec ) = @_; sub { my ( $f1 ) = @_; $curried_rec->( sub { $f1->( $f1 )->( @_ ) } ) }->( sub { my ( $f2 ) = @_; $curried_rec->( sub { $f2->( $f2 )->( @_ ) } ) } ) }