| handwaving
my $result = GetOptions( 'file=s' => \$infile,
                         'debug' => \$debug,
                         'verbose' => \$verbose,
                         'out=s' => \$outfile
              );

upchuck_and_die unless ( $file && $outfile ) ;

|
| stuff
| later on
sub upchuck_and_die {
     print "you must specify --infile=<file> and --outfile=<otherfile>\n";
     exit(-1);
}