I'm majoring in applied math and computation, I know pretty well that
computers are dumb xD

I think neither of you have understood what I wanted, so I'll give you an
example.
I have a lot of .xsl that generate pages and I want to make those pages
translatable. I migth have the file, for exemple, welcome.xsl:
 <?xml version="1.0" encoding="ISO-8859-1" ?>
<xsl:stylesheet version="1.0" xmlns:xsl="
http://www.w3.org/1999/XSL/Transform">
 <xsl:output method="html" indent="yes" encoding="iso-8859-1" />
 <xsl:template match="/">
<xsl:if test="welcome">
 <p>Bem-vindo</p>
</xsl:if>
 <ul>
<xsl:for-each select="elements">
<li>Coisa <xsl:value-of select="name" /></li>
 </xsl:for-each>
</ul>
</xsl:template>
 </xsl:stylesheet>
And I wanted to make this translatable, so I change this to
 <?xml version="1.0" encoding="ISO-8859-1" ?>
<xsl:stylesheet version="1.0" xmlns:xsl="
http://www.w3.org/1999/XSL/Transform">
 <xsl:output method="html" indent="yes" encoding="iso-8859-1" />
 <xsl:template match="/xml">
<xsl:if test="welcome">
 <p><xsl:value-of select="/xml/lang/_WELCOME" /></p>
</xsl:if>
 <ul>
<xsl:for-each select="elements">
 <li> <xsl:value-of select="/xml/lang/_STUFF" />  <xsl:value-of
select="name" /></li>
</xsl:for-each>
 </ul>
</xsl:template>
 </xsl:stylesheet>
And I create a languages/pt.php with:
 define('_LANG_WELCOME','Bem-vindo');
 define('_LANG_STUFF','Coisa');

I have a piece of php code that puts in the xml all the constants that
begin with "_LANG".

I have a lot of these .xsl and I need to go manually through them all to
find the strings that I want to make translatable. What I want this script
to do is, on my input put that <xsl:value-of select="/xml/lang/_STUFF"
/> thing on the place I select and append to the language file the
repective define();.