# If you'd like to omit non-matching lines from the result; add ';d' to the end of the expression.
sed -E 's/([0-9]{11}).+?(\s*[0-9].+)/$1xxxxxxxxxxxxxxxxxxxx$2/gm;t' <<< "01234567890Alice Stone 3978 Smith st...
01234567890Alice Stone3978 Smith st..."
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