projekt kivitendo

sub cross(&\@\@) {

  my $op = shift;

  use vars qw/@A @B/;

  local (*A, *B) = @_;    # syms for caller's input arrays

  # Localise $a, $b

  my ($caller_a, $caller_b) = do

  {

    my $pkg = caller();

    no strict 'refs';

    \*{$pkg.'::a'}, \*{$pkg.'::b'};

  };

  my $limit = $#A > $#B? $#A : $#B;    # loop iteration limit

  local(*$caller_a, *$caller_b);

 # This map expression is also the return value.

  map { my $b_index = $_;

    map { my $a_index = $_;

      # assign to $a, $b as refs to caller's array elements

      (*$caller_a, *$caller_b) = \($A[$a_index], $B[$b_index]);

      $op->();    # perform the transformation

    }  0 .. $#A;

  }  0 .. $#B;

}