#!/usr/bin/perl
use strict;
use warnings;
use Getopt::Std;

my $usage = "Usage; $0 [-t x] where x is
a time interval in minutes from 10 to 60.
If no interval is given, defaults to 1 hour (60 min).\n";

my %opts;
getopts ('t:',\%opts);
my $interval = $opts{t} || 60;
die $usage unless $interval == 10 .. $interval == 60;