>perl -we 'use strict; 

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,{});}'

Use of uninitialized value $test1 in concatenation (.) or string at -e line 1.
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