Thank you everyone. Someone from apple.com>Unix forum solved my problem. I needed to change the file permissions as below. 

old file permissions:
-rw-rw-rw-  34 root    wheel         807 Jun 24  2009 instmodsh
-rw-rw-rw-  34 root    wheel         807 Jun 24  2009 perldoc

[download]

I set the execute bit using:

sudo chmod +x /usr/bin/instmodsh /usr/bin/perldoc 
new file permissions:
-rwxrwxrwx  34 root    wheel         807 Jun 24  2009 perldoc
-rwxrwxrwx  34 root    wheel         807 Jun 24  2009 instmodsh

[download]

Now, it works!

In reply to Re^4: /usr/bin/instmodsh: Permission denied. by rnaeye
in thread /usr/bin/instmodsh: Permission denied. by rnaeye

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