On a Windows system (without binmode),

while (<$fh>) {
   # If the file contained lines ending with CRLF, $_ ends with LF
   # If the file contained lines ending with LF,   $_ ends with LF
   chomp;  # Removes LF
}
[download]

On other systems,

while (<$fh>) {
   # If the file contained lines ending with CRLF, $_ ends with CRLF
   # If the file contained lines ending with LF,   $_ ends with LF
   s/\r?\n\z//;  # Removes CRLF or LF
}
[download]

And since the latter works on Windows as well, you can just use it everywhere.

The only systems where this doesn't work are old Macs.