LTM: Multiple headers for "Request Header Insert"

If you have 11.4.0 or newer you could use LTM Policies to insert multiple HTTP headers via the GUI (or use iRules).

From the GUI...

Local Traffic->Policies->Policy List-> + (add)
Give it a name and select "http" in the "requires" section and click "Finished".
Add a rule to this policy..Call it something like "AddHeader".  
Leave the conditions section empty but modify the Actions section with the following fields:
target: http-header 
event: request 
action: insert 
parameters: name yourhttpheadername 
            value yourhttpheadervalue
Then add additional actions for each http header you want to insert..
Once you finished creating the LTM policy, simply assign it to your virtual server under the "resources" tab.