When decoding text, particularly when it came by way of Excel, you are likely to encounter \x{FEFF} appended to the first piece of text or another escaped character. This is a Byte Order Mark, and its purpose is to indicate something about the encoding of the text stream, usually that it’s UTF-8 or something like that.

To remove it, try one of the following, originally from here).

s/^\x{FEFF}//;
s/^\N{U+FEFF}//;
s/^\N{ZERO WIDTH NO-BREAK SPACE}//;
s/^\N{BOM}//;   # Convenient alias

In vim, you can remove it when you are saving the file:

:setlocal nobomb
:w

To ask vim whether there is a BOM:

:setlocal bomb?