What happens when you try to run it the way you want to run it?

Sometimes I've seen scripts fail because the shebang line has a trailing carriage return. You can find this if you run it through "od" or some other hex dump program.

$ head -1 good.pl | od -c
0000000  #   !   /   u   s   r   /   b   i   n   /   p   e   r   l  \n
0000020

$ head -1 bad.pl | od -c
0000000  #   !   /   u   s   r   /   b   i   n   /   p   e   r   l  \r
0000020 \n
0000021
[download]

You can strip out the carriage returns using perl this way:

perl -pi.bak -e 's/\r//g' my_script.pl
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If the script is supposed to have some carriage return in it, this will break it, but that's unusual. If it causes a problem, the above line creates a .bak file that you can revert to.