# If you'd like to omit non-matching lines from the result; add ';d' to the end of the expression.
sed -E 's/^(?:[a-z]|\d+)(?:\.\d+)*\.?\s*(?:\([A-Z]\.\d+(?:\.[A-Z]\.\d+)*\)\s*)?//gm;t' <<< "c.2 Employed population below international poverty line, by sex and age (%) Age: 15+
b.1 Employed population below international poverty line, by sex and age (%) Age: 15+
a.1 Employed population below international poverty line, by sex and age (%) Age: 15+
1. Employed population below international poverty line, by sex and age (%) Age: 15+
1.2 Employed population below international poverty line, by sex and age (%) Age: 15+
1.1.1 Employed population below international poverty line, by sex and age (%) Age: 15+
5.6.2 (S.1.C.1) Employed population below international poverty line, by sex and age (%) Age: 15+
5.6.2 (S.3) Employed population below international poverty line, by sex and age (%) Age: 15+
5.6.2 (S.4.C.13) Employed population below international poverty line, by sex and age (%) Age: 15+"
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