<xsl:transform xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:sap="http://www.sap.com/sapxsl" version="1.0">

  <xsl:output encoding="utf-8" indent="no" method="xml" omit-xml-declaration="yes"/>
  <xsl:strip-space elements="*"/>

  <xsl:template match="ROOT">
    <xsl:param name="P" sap:type="string"/>
    <debug>
      <xsl:value-of select="$P"/>
    </debug>
  </xsl:template>

</xsl:transform>

DATA:  lt_xslt_source TYPE abap_trans_srcbind_tab,
       ls_xslt_source TYPE abap_trans_srcbind,
       lv_data        TYPE string,
       lv_value       TYPE string VALUE 'TEST',
       lv_xml         TYPE string.

lv_data = ''.
ls_xslt_source-name  = 'ROOT'.
GET REFERENCE OF lv_data INTO ls_xslt_source-value.
APPEND ls_xslt_source TO lt_xslt_source.

CALL TRANSFORMATION ztest4 SOURCE (lt_xslt_source)
                           RESULT XML lv_xml
                           PARAMETERS P = lv_value.

WRITE ''.

<debug>TEST</debug>

<debug></debug>

<xsl:transform xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:sap="http://www.sap.com/sapxsl" version="1.0">

  <xsl:output encoding="utf-8" indent="no" method="xml" omit-xml-declaration="yes"/>
  <xsl:strip-space elements="*"/>

<xsl:param name="P" sap:type="string"/>

  <xsl:template match="/">
    <debug>
      <xsl:value-of select="$P"/>
    </debug>
  </xsl:template>

</xsl:transform>