libxml2-dev - 2.9.10+dfsg-6.7+deb11u5 main

XML is a metalanguage to let you design your own markup language.
A regular markup language defines a way to describe information in
a certain class of documents (eg HTML). XML lets you define your
own customized markup languages for many classes of document. It
can do this because it's written in SGML, the international standard
metalanguage for markup languages.
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Install this package if you wish to develop your own programs using
the GNOME XML library.