sub test{
  my $i = shift;
  my $params = shift;
  my $test1 = $params->{test} if exists $params->{test};
  print "test1 after hash assignment:\t\t$test1\n";
  $test1 = $i if ! defined $test1;
  print "i = $i\ttest1 after defaulting to i:\t$test1\n";
}

for my $i(0..3){
  &test($i,{});
}

##</code><code>##

Output: 
Use of uninitialized value $test1 in concatenation (.) or string at test.pl line 19.
test1 after hash assignment:		
i = 0	test1 after defaulting to i:	0
test1 after hash assignment:		0
i = 1	test1 after defaulting to i:	0
test1 after hash assignment:		0
i = 2	test1 after defaulting to i:	0
test1 after hash assignment:		0
i = 3	test1 after defaulting to i:	0
<br>