How to concatenate multiple strings in android XML?

Problem
I would like to be able to do something like that in Android XML code:

<string name="title">@string/app_name test</string>
<string name="title2">@string/app_name @string/version_name</string>

Regarding first line of code compiler shows this error

No resource found that matches the given name (at 'title' with value '@string/app_name test')

and regarding second line of code compiler shows this error

No resource found that matches the given name (at 'title2' with value '@string/app_name @string/version_name')

Question
Does anybody know how to concatenate multiple strings in Android XML?

Rationale
It is bad practice to duplicate variable values in many places of code (in this case XML).