hm, at first sight i would say that $last_range, $first_day should be initialised outside the for-loop. look at and execute this:

for ( 1 .. 10 ) {
    my $i;
    $i++;
    print $i;
}
print "\n";
my $i;
for ( 1 .. 10 ) {
    $i++;
    print $i;
}
print "\n";
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