fionbarr:

You need to use scalar(@{$a[0]}) to get 3. Your array contains only one element, the array reference. So if you want 3, you need to ask the referenced array for its size, not the container. Perhaps this example will help:

$ cat t.pl
#/usr/bin/perl
use strict;
use warnings;
use Data::Dumper;

my @a = (1, 2, 3);

print "Size of a: ", scalar(@a), "\n";
print Dumper(\@a),"\n";

my @b = [0, 1, 2];
print "Size of b: ", scalar(@b), "\n";
print Dumper(\@b),"\n";

print "Size of b[0]: ", scalar(@{$b[0]}), "\n";
print Dumper($b[0]),"\n";
[download]

which gives us:

$ perl t.pl
Size of a: 3
$VAR1 = [
          1,
          2,
          3
        ];

Size of b: 1
$VAR1 = [
          [
            0,
            1,
            2
          ]
        ];

Size of b[0]: 3
$VAR1 = [
          0,
          1,
          2
        ];
[download]

...roboticus

When your only tool is a hammer, all problems look like your thumb.