It's a cheap solution, but I would probably write a wrapper.

sub setresuid {
    # force @_ to have three elements
    $#_ = 2;

    # replace undefs in @_ with -1
    for ( @_ ) {
        $_ = -1 if ! defined $_;
    }

    # magic goto the real setresuid
    goto &real_setresuid;
}
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