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my @opts = qw( a b ... z );
GetOptions(
...
for my $opt (@opts) {
   die("...\n") if !exists($opts{$opt});
}

my %opt_defs = (
    ( map { $_ => "$_=s" } qw( a b ... ) ),
...
for my $opt (keys(%opt_defs)) {
   die("...\n") if !exists($opts{$opt});
}