perldoc -f my
A "my" declares the listed variables to be local
(lexically) to the enclosing block, file, or "eval".

##</code><code>##

$ perl
use strict;
use warnings;

{
  package one;
  my $var = 1;
}

{
  package two;
  my $var = 5;
}

package main;

print "$var\n";
Global symbol "$var" requires explicit package name at - line 16.
Execution of - aborted due to compilation errors.