I was sent the following code (slightly edited): 
#!/usr/bin/perl
# fill two 25 x 25 arrays with zeros, then modify a couple of cells
my @PP = my @OO = (1..25);

# fill PP and OO arrays with zeros
for($rr = 0; $rr < 25; $rr++) {
  for($cc = 0; $cc < 25; $cc++) {
    $PP[$rr][$cc] = 0;
    $OO[$rr][$cc] = 0;
  }
}

# uncommenting the below shows array PP zeroed out
for my $row (@PP) {
 print join(",", @{$row}), "\n";
}

print "\nAfter:\n";

$OO[1][1]=1; # just so it will be easy to spot
$OO[2][2]=2;
$OO[3][3]=3;
$OO[4][4]=4;
# code below. shows the values inserted into array OO cells appearing 
+in PP cells ???

print "PP array\n";
for my $row (@PP) {
print join(",", @{$row}), "\n";
}

print "\nOO array\n";
for my $row (@OO) {
print join(",", @{$row}), "\n";
}
exit;

[download]
When run, both arrays are the same. With the first active line changed to my @PP = my @OO; with no initialization, the code works as expected; i.e., the @PP array is unchanged. Why the difference??

In reply to Array wierdness by lgp

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