<DATA> is not a filehandle, it's the <> I/O operator (aka readline) applied to the bareword filehandle DATA. $csv->getline(DATA) may work in your code because you don't have strict turned on (which can cause strange and hard-to-analyze bugs), but since you should always Use strict and warnings, you should use the glob notation to pass bareword filehandles as arguments, i.e. $csv->getline(*DATA). For files you open, nowadays you should always use lexical filehandles - "open" Best Practices.

Minor edits shortly after posting.

Update in response to your edit: Relevant reading is Symbol Tables, Typeglobs and Filehandles, and Passing Symbol Table Entries (typeglobs) (and perlref for globrefs).

In reply to Re: Filehandles and CSV_XS (updated) by haukex
in thread Filehandles and CSV_XS by Melly

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