Note, however, that if you had warnings on (use warnings;), you would have seen something like this when executing example 2:

Use of uninitialized value in concatenation (.) or string at ./test.pl
+ line 5.
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This is because you refer to a value ($var) which, while it is within the current scope, has never been set to any value (it is still undef). I find that such warnings are often an indicator that my code is doing something I don't expect or haven't prepared for.