[TYPO3] globalvars, GP and checkbox arrays

[Claudio Strizzolo]

Hi all,
Maybe a stupid question, but I couldn't find an answer in the 
documentation (TSref and such).
I need to set up a condition in TS, depending on a value assigned to a 
field which is supplied through a form. Normally this would work:

[globalString = GP:Vehicle=car]
  (...)
[global]

Unfortunately, the field in the form is actually an array filled with 
data supplied through checkboxes:

<input type="checkbox" name="Vehicle[]" id="Vehicle_train" value="train" /
>Train
<input type="checkbox" name="Vehicle[]" id="Vehicle_car" value="car" />Car
<input type="checkbox" name="Vehicle[]" id="Vehicle_bus" value="bus" />Bus

In this case I don't know how to check for such a value. I tried with:

[globalString = GP:Vehicle=car]

but this obviously doesn't work because Vehicle is not a string.
I can't even check using array indexes, because I do not know which 
elements of the array have been filled:

[globalString = GP:Vehicle|0=car]

"car" might be at position 0 in the array if "train" was checked too, or 
"1" if it were the first option to be selected, so I can't know which 
field must be checked. And I have a large number of possible checkboxes, 
then I wouldn't like using a dirty OR format like:

[globalString = GP:Vehicle|0=car][globalString = GP:Vehicle|1=car]
[globalString = GP:Vehicle|2=car] (...)

I can't replace the checkboxes with radio or such too, because more than 
one field can be checked at the same time.
Any hints?
Thanks in advance

Claudio