# guess to set $/ to correct linebreaks
# untested code.

local $/ = \1000; # read first 1000 bytes
local $_ = <$file>;
my $newline;
for my $test ("\015\012","\015","\012") { # match various newline chars, default to unix
  $newline = $test;
  last if /$test/;
}
local $/ = $newline;
seek $file,0,0; # rewind to start of file