Depend and if/else in transaction emails in Magento 1

Question

we are investigating some checks in our transactional emails or newsletters and looking at http://merch.docs.magento.com/ce/user_guide/store-operations/email-transactional.html

where we find the code below.

My question: can we use this DEPEND or IF to check the existence or emptiness of a variable? Something like

{{if customer.getFirstname()}} 
  {{var customer.firstname}} 
{{else} 
  {{var customer.name}} 
{{/if}}

Example from link

Depend Condition

{{depend order.getIsNotVirtual()}}

{{/depend}}

{{depend salable}}

{{/depend}}

- If Condition

{{if order.getIsNotVirtual()}}

{{else}}

{{/if}}

(else is optional)

Answer 1

This is exactly the purpose of {{depend}} and {{if}}. The only difference between them is that {{if}} supports an {{else}} statement.
{{depend}} is just as an {{if}} without an {{else}}.
To see how they work refer to Varien_Filter_Template::dependDirective() and Varien_Filter_Template::ifDirective().