Your shell script is calling bash to execute your content.

$ echo $SHELL
/bin/bash
$ setenv
No command 'setenv' found, did you mean:
 Command 'netenv' from package 'netenv' (universe)
setenv: command not found

$ csh
% setenv | tail -n 1
_=/bin/csh
%
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In the header of your shell script you need to declare your executing shell - "#!/bin/csh " or where ever it is located on your system.

$ cat test
#!/bin/csh
echo "trying to use setenv"
setenv | tail -n 1
$ ./test
trying to use setenv
_=./test
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