i can't answer your question, but i recommend you check for errors from prepare as well. (one possibility is that one of your keys is not a column of $table, but i would expect to see an error trying to call execute on an undefined value.)

my $sth = $dbh->prepare($sqlstatement) 
    or die "cannot prepare: $DBI::errstr";
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unrelated, but you can also simplify the top part of your function a bit:

my @values  = values %$data;
my $keylist = join ',', keys %$data;
my $qlist   = join ',', ('?') x @values;
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