Yes, you need to used Xslt, either Inline Xslt in a scripting finctoid or a custom Xslt file
<xsl:for-each select="inputrecord">
<xsl:variable name="var:v1" select="'firstname' + ./position()" />
<xsl:element name="{$var:v1}">
<xsl:value-of select="."/>
</xsl:element>
</xsl:for-each>
Not sure of concatenation rules with Xpath, might have to look that one up.