$ perl -e 'open $fh, "." or die $!; $/=undef;$x=<$fh>; warn $^O, " ", length $x'
freebsd 15360 at -e line 1, <$fh> chunk 1.

$ perl -e 'open $fh, "." or die $!; $/=undef;$x=<$fh>; warn $^O, " ", length $x'
linux 0 at -e line 1.