# If you'd like to omit non-matching lines from the result; add ';d' to the end of the expression.
sed -E 's/\b(?<!!)[A-Z]{1,2}[0-9]/sheet_turnover!$0/g;t' <<< "=+(sheet_factory_costs!A17/sheet_employees!D23)+T12+W12
=+(sheet_factory_costs!A17 / sheet_employees!D23)+sheet_turnover!T12+sheet_turnover!W12"
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