#!/usr/bin/perl -w
use strict;    #<- very important.

my $foo = 3;  # $foo has a value of 3, and is seen by the compiler.

{

my $bar = 5;  # $ bar life is limited to the block.
print "$bar\n"; # you get 5.
print "$foo\n";	# you get 3.

}
print "$bar\n"; # <- compiler gives error.$bar does not exsist (kind of).
print "$foo\n";	# you get 3.