Yeah, I meant 5.10, not 5.8.+. Sorry. In an Email conversation with John he agrees that _largefile should not have an effect on setpos/getpos. Also, his comment on a possible bad print in the test turned out not to apply.
fwiw... In my world 2Gb is NOT a large file anymore. My customers toss around 100GB sequential files and 200+ GB indexed files. You want to treat carefully touching such files, as any mistake can set a process spinning for hours! Testdrive: $ perl -"V:uselargefiles" uselargefiles='undef'; Cheerio, Hein.