Well, meanwhile I have found a solution:
my $insertstuff = join ", ", map {Encode::encode("iso-8859-1", Encode::decode("utf8",$_)) } @insert_vals;
Encode::_utf8_on($insertstuff);
Turning utf8 on (not off as I thought first) works.
Rolf
my $insertstuff = join ", ", map {Encode::encode("iso-8859-1", Encode::decode("utf8",$_)) } @insert_vals;
Encode::_utf8_on($insertstuff);