# If you'd like to omit non-matching lines from the result; add ';d' to the end of the expression.
sed -E 's/^.+?\/p\/[^\/]+\///;t' <<< "https://www.reading.am/p/4Nix/http://www.nejm.org/doi/full/10.1056/NEJMsa1202099#t=article"
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