In what sense is this a Perl(-related) question?

I doubt that there are very many who would want to see "the entire data file" -- perhaps you could present a snippet of the data (or, if you're worried about sensitive contents, make up pseudo-data that has similar properties, e.g. "random" digits, letters and punctuation positioned to be equivalent to the actual data).

It seems unlikely that "%s" etc have anything to do with unicode. These designations are probably intended for programmers who know the "printf" function (which should include you -- you may want to refer to docs or other references regarding this standard C library function; it is available in Perl, of course -- see "perldoc -f printf" -- but the Perl manuals take it for granted that you already know about the C function that it emulates).

In any case, your guess about "%s" referring to a string is probably right; "%d" probably refers to a signed decimal integer value, "%u" an unsigned decimal integer, and "%04x" an integer in hexidecimal format (padded with leading zeros to provide a constant width of four digits).

If you try something with Perl, and it doesn't do what you want or expect, let us know...