Dear Monks, I present a bewildering consequence of postfix if() statements and variable assignment. Please help me find enlightenment!

A colleague's code both scopes a variable and tests another in postfix. I would expect this to trap the value inside the scope of the if() block, but for some reason I cannot see, it is persisting in style of a closure, and while the debugger reports undefined values in every iteration, print somehow finds meaning in the same scalar.

sub test{ 
  my $i = shift; 
  my $params = shift;  

  my $test = $params->{test} if (exists $params->{test}); 
  print "test after hash assignment:\t\t$test\n"; 
  $test = $i unless (defined $test);
  print "i = $i test after defaulting to i:\t$test\n";
} 
for my $i (3..5){ &test($i) }
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If I scope the test properly, everything works as I expect, but with this in-line scoping, it seems to be both defined and not. Note that $params is never set.

test1 after hash assignment:
i = 3    test1 after defaulting to i:    3
test1 after hash assignment:        3
i = 4    test1 after defaulting to i:    3
test1 after hash assignment:        3
i = 5    test1 after defaulting to i:    3
[download]

Please help me to understand the execution order of that postfixed if line.