I can't use Spreadsheet::Read as I have to input missing zip codes

You apparently misunderstood me. I wasn't saying "use Spreadsheet::Read instead of Excel::Writer::XLSX ". I was saying "use Spreadsheet::Read instead of using a manual open and a while(<FH>) loop to read the old spreadsheet in, and continue to use Excel::Writer::XLSX as the way to write your new file out".

I just brought up Text::CSV (*) because you seemed to be treating the spreadsheet you were reading as a text file, and CSV is the only pure-text spreadsheet format that I know about, so I thought maybe you were confused about file formats. Since your input file is actually named SRC185.xlsx then it is not a CSV file and you cannot use Text::CSV . (*: CSV is a text-based spreadsheet; CVS is a pharmacy chain or a version-control system that served as a precursor to SVN; VCS is the generic abbreviation for version control software; there are too many valid anagrams of that TLA.)

So in case it wasn't stated succinctly enough yet:

• To read the source spreadsheet SRC185.xlsx you should use Spreadsheet::Read
• To write the output spreadsheet Output2022.xlsx you should continue to use Excel::Writer::XLSX

Thank you for clarifying that for me, we use csv's alot so I may play around with that module here eventually, but for this purpose I don't need to turn it into a cvs yet in the process for convenience. Thats something I will probably be working towards eventually though.