Problem with #!/usr/bin/env bash

A few months ago, I created a bunch of Linux shell scripts, and they all gave me an error message.  The first line of a script, for example foo.sh, was

#/usr/bin env bash 

When I ran this script with "./foo.sh", I got this error message

./foo.sh: line 1: #!/usr/bin/env: No such file or directory

This drove me nuts for a while, and I finally figured out the problem.  Although the line looked just fine in vi, I ran

head -1 foo.sh | hd

And got 

00000000 ef bb bf 23 21 2f 75 73  72 2f 62 69 6e 2f 65 6e  |…#!/usr/bin/en|
00000010 76 20 62 61 73 68 0a                                                 |v bash.|
00000017

It turns out that those first three bytes are a UTF-8 Byte Order Mark (BOM), which characterizes the character set that follows.  Although vi hides this, you can remove the bytes with ":set nobomb".  I also now see that TextWrangler shows "Unicode (UTF-8, with BOM)" at the bottom, and you can click to change it to "Unicode (UTF-8)".  I must have somehow used some text editor to create the first shell script with the BOM, and when I copied it to create the other ones, the three bytes propagated like a virus.