# If you'd like to omit non-matching lines from the result; add ';d' to the end of the expression.
sed -E 's/^StartWord\R+\K.*?\R(?=\R*^StopWord\R)//gms;t' <<< "Delete this text De l e te this text
StartWord
Apples Oranges
Pears Grapes
StopWord
Delete this text Delete this text
StartWord
Peas Carrots
Peas Carrots
StopWord
Delete this text Delete this text
"
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