while ( my ( $k, $v ) = each %opts ) {
    state %dispatch = (
        h => sub{...;},
        v => sub{ ++$verbose;},
        i => sub{ $infile = $v; },
    );

    die "*** BUG: no handler for -$k.\n" if !exists $dispatch{$k};
    &{$dispatch{$k}};
}