The '=' in 'refresh=i' doesn't mean that 'refresh' is a mandatory
option to the program. It means that, if 'refresh' is supplied,
the *integer argument* is mandatory. So you can't just have
$ foo.pl --refresh
An argument to 'refresh' is mandatory.
I don't think there *is* a way to indicate that an option is
mandatory (ie. that 'refresh' must be provided as an option).
And since 'refresh' may not be provided, the
$REFRESH = 10
sets the default value for 'refresh' to 10. And it can be overriden
on the command line with '--refresh'.