use strict;
{
    my $foo = 2;
    {
        my $foo = 1;    # masks outer $foo
        my $bar = $foo;
        print "foo is '$foo'\n"; # foo is '1'
    }
    print "foo is '$foo'\n";     # foo is '2'
    print $bar; #                # error, $bar not visible here
    my $foo;                     # warning: $foo already declared
                                 # as lexical in this scope.
}
print "foo = $foo\n";            # error, $foo not visible here