Question : PowerShell - Array of arrays

I have data in a pipeline from which I want to create an array of arrays like, for example:
  (a, XXa), (b, XXb), (c, XXc)
I don't want to use a pre-declared multi-dimensional array because it is messy and I don't know in advance how big it will need to be.

This code does not work - is gives a length of 6
$arrayOfArrays = ("a","b","c") | %{($_, "XX$_")}
# Check if it worked:
"arrayOfArrays[2] = " + $arrayOfArrays[2]
"Length = " + $arrayOfArrays.length


This code works but it is messy:
$tmp = @(1)
$arrayOfArrays = @()

("a","b","c") | %{ $tmp[0] = ($_, "XX$_"); $arrayOfArrays += $tmp;}
# Check if it worked:
"arrayOfArrays[2] = " + $arrayOfArrays[2]
"Length = " + $arrayOfArrays.length

Is there a better way?

Answer : PowerShell - Array of arrays

Two fellow MVPs provided this explaination (Kirk and Karl)

######################################
The pipeline (and certian other operations) will try to Strip an array(or any collection/Ienumerable), so that it can push it down the pipeline one item at a time.. the , just wraps something into an array.. so often if you already have an array you use the , to put that array inside an array , so that when the pipeline strips it, it just pushes the original array down the pipeline as ONE item. look at this
,,,(
1..5)
You will notice the 5 element array is inside a one element array which is inside a one element array which is inside a one element array..
 
now run each of these
,,,(
1..5) | % { $_ }
,,,(1..5) | % { $_ } | % { $_ }
,,,(1..5) | % { $_ } | % { $_ } | % { $_ }
 
you'll see that the "container arrays" get strip at each pipeline level, with the Last line, having been run through a pipeline boundary 3 times, you get the final container array stripped, and the pipeline gets the the items stripped and pushed down one at a time..