As Corion already pointed out, but more explicitly stated:

my @in_vals = (1,2,3);
my $in_placeholders = join ',', ('?') x @in_vals;
my $sth = $dbh->prepare(qq{select * from foo where bar=? and baz in ($
+in_placeholders)});
$sth->execute(1, @in_vals) or die $dbh->errstr;
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