For those wondering here the docs: -T

• -T File is an ASCII or UTF-8 text file (heuristic guess).

• -B File is a "binary" file (opposite of -T).

...

The -T and -B tests work as follows. The first block or so of the file is examined to see if it is valid UTF-8 that includes non-ASCII characters. If so, it's a -T file. Otherwise, that same portion of the file is examined for odd characters such as strange control codes or characters with the high bit set. If more than a third of the characters are strange, it's a -B file; otherwise it's a -T file. Also, any file containing a zero byte in the examined portion is considered a binary file. (If executed within the scope of a use locale which includesLC_CTYPE , odd characters are anything that isn't a printable nor space in the current locale. ) If -T or -B is used on a filehandle, the current IO buffer is examined rather than the first block. Both -T and -B return true on an empty file, or a file at EOF when testing a filehandle. Because you have to read a file to do the -T test, on most occasions you want to use a -f against the file first, as in next unless -f $file && -T $file .

Consequently I would check if the new Perl installation has another locale setting.

Like others said, give us an example input to reproduce the problem.