XSLT is a language, which can transform an XML input (with XSLT 2.0, we can take a Text input as well) to various kinds of outputs (like XML, HTML and Text).

I didn't know about the text input, and that could be very useful for

me. Could you provide any online tutorial about that?

Look for the unparsed-text() function.  With the new regex capabilities
of XSL2, xsl is fast becoming an alternative to  lexer/parser generators
for quick and dirty stuff for me.  For example take a look at this CSV
to XML stylesheet.  While not a tutorial per se, I believe it
illustrates the point quite well.

http://andrewjwelch.com/code/xslt/csv/csv-to-xml_v2.html

Thanks,

~Chris