# If you'd like to omit non-matching lines from the result; add ';d' to the end of the expression.
sed -E 's/(\b(DIN)|(DIN EN)|(DIN EN ISO)|(DIN ISO)|(DIN-EN)|(DIN-EN-ISO)|(DIN-ISO)|(EN)|(IEC)|(ISO)|(NEN)|(NEN‑EN)|(NEN‑EN‑IEC)\b)(\s)(\d)/$1‡$3/gm;t' <<< "You can find the specifications in DIN 12345, DIN EN 12345, DIN EN ISO 12345, DIN ISO 12345, DIN-EN 12345, DIN-EN-ISO 12345, DIN-ISO 12345, EN 12345, IEC 12345, ISO 12345, NEN 12345, NEN‑EN 12345, NEN‑EN‑IEC 12345."
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