Here is a simple brief example, but like dragonchild says, to get the complete picture you should really get a Perl book. Personally I would recommend you borrow, steal or buy the "Camel" book from O'Reilly. It will fill you in on all the stuff necessary to get you going.
use strict;
#declare the variable $foo before using
my $foo;
$foo = 'hello world';
print $foo;