XSLT processing-instruction: grab everything after

I have a XML file which looks like this:

<block>
  
    <?foo bar1?>
  
        <section>
          A
        </section>
        <section>
          B
        </section>

    <?foo bar2?>
  
        <section>
          C
        </section>
        <section>
          D
        </section>

</block>

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I want the output to be something like this:

A
B
foobar1 stuff

C
D
foobar2 stuff

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My XSLT code looks something like this:

<xsl:template match="block">
  <xsl:apply-templates select="* | processing-instruction('foo') "/>
</xsl:template>

<xsl:template match="processing-instruction('foo')">
somehow process everything that follows, up to next "foo" processing-instruction, then output "foobar1 stuff"
</xsl:template>

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My problem is how to process everything following the "foo" processing-instruction, up to the next "foo" processing-instruction, and then output "foobar1 stuff".

Is this even possible?