The existing paths are valid for Debian, alternative paths are necessary
for Fedora and RHEL/CentOS.
# removes iso-entites sub directory after doing make install.)
#
$ENV{SGML_CATALOG_FILES} .= (defined $ENV{SGML_CATALOG_FILES} ? ":" : "") .
+ "$main::prefix/share/sgml/sgml-iso-entities-8879.1986/catalog:";
"$main::prefix/share/sgml/entities/sgml-iso-entities-8879.1986/catalog";
$ENV{SGML_CATALOG_FILES} .= ":$main::DataDir/linuxdoc-tools.catalog";
$ENV{SGML_CATALOG_FILES} .= ":$main::/etc/sgml.catalog";