use utf8;

print($fh chr(0x40));     # Happens to work
print($fh chr(0xC9));     # Generates broken output
print($fh chr(0x2660));   # Warns

binmode($fh, ':utf8');
print($fh chr(0x40));     # Ok
print($fh chr(0xC9));     # Ok
print($fh chr(0x2660));   # Ok