in reply to Re: check if file is executable by user/group/world?
in thread check if file is executable by user/group/world?

This is why you should use warnings and strict in your code. With warnings turned on you should get next warning:

Useless use of array element in void context at ./file_change_mode.pl line 12.

Reason why this is happening you can see in perlfunc.

You could write:
chmod(($mode | S_IXOTH), $ARGV[0]);