which means you won't have much use of nested loops with map

Could you explain what you mean there? map localizes $_, so nested maps are not a problem. Code like the following (admittedly contrived) snippet works as expected ($_ is not clobbered by the inner map):

my @list = (
    ["Barney", "Rubble"],
    ["Fred", "Flintstone"],
    ["Betty", "Rubble"],
    ["Wilma", "Flintstone"]
);

map {
    say "Outer map before: @$_";
    map { 1 } @$_;
    say "Outer map after : @$_";
} @list;
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But perhaps there's other pitfalls, so I'd be grateful for any enlightenment.

The problem happens when you need to use the $_ from the outer map in the inner map, as in the following contrived example:

my %tree = (
            child1 => {},
            child2 => {
                       grandchild1 => { brood3 => {} },
                       grandchild2 => { brood1 => {}, brood2 => {} },
                      },
           );

say for 'Grandchildren:',
    map {
        my $x = $_;   #   <--- remove me!
        "$_: " . (ref $tree{$_} ? join ', ' =>
                                  map keys %{ $tree{$x}{$_} },
                                      keys %{ $tree{$_}     }
                                : q())
    } keys %tree;
[download]

لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ

> Could you explain what you mean there?

I was talking about chaining maps or fors to simulate nested foreach loops.

I.o.w. list comprehensions are very hard to implement in Perl without nested blocks.

e.g. try to implement this Python example for "Pythagorean triples" w/o nesting

>>> [(x,y,z) for x in range(1,30) for y in range(x,30) for z in range(
+y,30) if x**2 + y**2 == z**2]

[(3, 4, 5), (5, 12, 13), (6, 8, 10), (7, 24, 25), (8, 15, 17), (9, 12,
+ 15), (10, 24, 26), (12, 16, 20), (15, 20, 25), (20, 21, 29)]
[download]

Cheers Rolf

_{(addicted to the Perl Programming Language and ☆☆☆☆ :)}

Ah, yes, I see what you mean.