This tells why:

use strict;
use warnings;
use Data::Dumper;

my $a = [[0,1,2], [10,11,12]];
print \$a->[0][0], "\n";
print \$a->[0][1], "\n";
print \$a->[0][2], "\n";
print \$a->[1][0], "\n";
print \$a->[1][1], "\n";
print \$a->[1][2], "\n";
print "=======\n";
print \$_, "\n" for map @$_, @{$a};#one of your way
print "=======\n";
foreach (@$a) { print \$_, "\n" foreach @$_ }#your other way

[download]

Result, see how the 3rd set is the same as the 1st one, but the 2nd set stands alone:

SCALAR(0x15551a4)
SCALAR(0x15551b0)
SCALAR(0x15551c8)
SCALAR(0x155abd4)
SCALAR(0x155500c)
SCALAR(0x1571284)
=======
SCALAR(0x15712c0)
SCALAR(0x1571290)
SCALAR(0x15551d4)
SCALAR(0x15712e4)
SCALAR(0x15712d8)
SCALAR(0x15712cc)
=======
SCALAR(0x15551a4)
SCALAR(0x15551b0)
SCALAR(0x15551c8)
SCALAR(0x155abd4)
SCALAR(0x155500c)
SCALAR(0x1571284)

[download]

In reply to Re: $_ and list flattening with map() by pg
in thread $_ and list flattening with map() by liz

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