You need to put your Perl script into a text file, and not type it immediately into the shell (the "terminal" you see).

To run your very first Perl program immediately, use this in the shell:

perl -we 'print "Hello World!"'
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but for longer scripts, create them using a text editor like TextPad or TextMate or in my example vi:

> vi myscript.pl
... enter the script
> ls -l myscript.pl
-rw-r--r-- 1 corion corion 96 19. Feb 18:09 myscript.pl
> perl -w myscript.pl
... output of the script
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vi is a versatile text editor, and it likely already is installed on your Mac, but it is not very friendly for a beginner just starting out. Most likely there is a friendly text editor using the OSX GUI included with OSX, but I don't know it. vi has the huge advantage of being available almost everywhere , which is why it helps to have knowledge about it in your toolbox. The two most important things to know about it are the command :q! which quits vi without saving, and :wq, which saves and then quits it.