So I'm just starting out with perl (literally just got the book for learning it yesterday) and one of the exercises, was making this program in text editor in ubuntu:
#!/usr/bin/perl
print "Hello, world!\n";

then I went and saved it and it said I have to identify it as an executionable file or something like that. Here is the full paragraph:

You may also need to do something so that your system knows it’s an executable program (that is, a command). What you’ll do depends upon your system; maybe you
won’t have to do anything more than save the program in a certain place. (Your current
directory will generally be fine.) On Unix systems, you mark a program as being executable using the chmod command, perhaps like this:
$ chmod a+x my_program



I entered that phrase: chmod a+x my_program
((the file was called my program, I named it that))

and terminal gave me this: chmod: cannot access 'my_program' : no such file or directory

and I tried renaming the program with a space and with the underscore, and placing it in different places like my documents, but it just keeps saying no such file or directory. Please help!!!!