Usage() && exit if grep{not exists $args->{$_}}@mandatory;

##</code><code>##

#!/usr/bin/perl -w
use strict;
use Getopt::Declare;

my $args = Getopt::Declare->new(<<'SPEC');
    -x <x:n>		x coord (real) [required]
    -y <y:n>		y coord (real) [required]
    -z <z:n>		z coord (real)
                        {print "Processing in three dimensions\n"}
SPEC

#rest of program...

__END__