I filed an enhancement report since if the workflow conditional facility does not appear to exist in Galaxy:

-------- Original Message --------
Subject: Workflows with conditional statements
Date: Wed, 18 May 2011 10:31:21 +1000
From: Florent Angly <florent.angly@gmail.com>
To: galaxy-user@lists.bx.psu.edu <galaxy-user@lists.bx.psu.edu>

Hi all,

I was wondering if there is a way to put conditional statements in a 
Galaxy workflow.

This would be useful, for example, in the case of a workflow that has an 
optional advanced option that the user can click. This advanced option 
would add some extra steps to the data processing.

Another example of how this could be useful is if inside a workflow, the 
data needs to be processed differently based on the results of previous 
workflow steps. Say, you have a worflow that takes some sequences, and 
calculate their average length. Using a conditional statement, the 
workflow would put the data through DeBruijn assembler if the reads are 
small, but through a traditional Overlap-Layout-Consensus assembler if 
the reads are long.

Are conditional statements possible in Galaxy workflows and I just don't 
know how to use them?