my $temp = "a";

sub test {
   my $temp = $test;
}
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please read the link provided about Coping with Scoping and please use <code> tags!

update

Basically does a my variable (aka lexical) belong to the surrounding '{ BLOCK }'.

A sub's (or an if's) body is a { BLOCK } and the file itself (i.e w/o surrounding curlies) is practically the top-level block.