It is easy to mix different methods to define HTML headers in PD4ML.

So first please take a look to the following topic:

In the code
[language=xml:26hdax88] <%=myVar%> [/language:26hdax88]
<%=myVar%> will be substituted with myVar value before the document is passed to PD4ML. So from PD4ML perspective it is going to be a static text (value). The only variable dynamically changes its value from page to page is $[page]

To define different headers for different pages you need to do something like that:
[language=xml:26hdax88] <%=myVar%> <%=myAnotherVar%> yet another var or static text [/language:26hdax88]