# If you'd like to omit non-matching lines from the result; add ';d' to the end of the expression.
sed -E 's/(?:^<[^\n<>]+>\h+<[^<>\n]+>\h+"|\G(?!^))[^_\n]+\K_(?=[^"\n]*")/ /gm;t' <<< "<http://dbpedia.org/resource/Animalia_(book)> <http://dbpedia.org/property/author> \"Graeme_Base\" .
<http://dbpedia.org/resource/Animalia_(book)> <http://dbpedia.org/property/illustrator> \"Graeme_Base\" .
<http://dbpedia.org/resource/Animalia_(book)> <http://dbpedia.org/property/illustrator> \"Graeme_Base_test1_test2\" ."
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for SED, please visit: https://www.gnu.org/software/sed/manual/html_node/The-_0022s_0022-Command.html