# If you'd like to omit non-matching lines from the result; add ';d' to the end of the expression.
sed -E 's/(\|(?>opening|insert|ending)\=)//gm;t' <<< "|mechanics={{mecha|p=GAT-04 Windam}}{{mecha|p=ZGMF-X23S Saviour Gundam}}{{mecha|p=Neutron Stampeder}}|opening={{track|p=Ignited}}
|insert={{track|p=Mizu no Akashi}}
|ending={{track|p=Reason}}}}"
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