Sometimes I wish that Perl could be even more sensitive about this, and issue the same sort of warning for cases like:

my $variable = "current value";

while ( whatever() ) {
   ...
   my $variable = "new value";  # if "my" was just typed by habit here
   ...
}

print $variable;  # then there's probably a bug when we get here
[download]

At present, perl does not warn about that sort of situation, and on the whole, it's probably better that it doesn't. So I just have to watch myself...