You shouldn't prompt the user for value he/she doesn't need to enter.

You probably meant to do something like this:

my $beacon     = shift @ARGV;
my $begin_time = shift @ARGV;
my $end_time   = shift @ARGV;
my @DAYS       = @ARGV;
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This will remove the first three elements of @ARGV and assigns the rest to @DAYS.

See shift for details.