Rebuild the current version of the source RPM: ftp://xmlsoft.org/libxslt/libxslt-1.1.26-1.src.rpm This is the preferred way of updating.

If that fails, download the source tarball ftp://xmlsoft.org/libxslt/libxslt-1.1.26.tar.gz and configure it to install in /usr/local.

    ./configure --prefix=/usr/local
    make && make install
[download]

XML::LibXSLT's Makefile.PL looks for the xslt-config binary to automatically configure the INC and LIBS MakeMaker parameters, so add /usr/local/bin to the path if needed.

An upgrade involves running make uninstall in the libxslt build directory, then installing the newer version, and again taking care of the Perl modules depending on the library. As you can imagine, even with putting /usr/local under revision control beforehand, this is still uncomfortable and error-prone. Use the checkinstall tool automate building custom RPMs.