==== Short answer (updated)

there is no DBI/SQL-placeholder for lists (unfortunately)

==== Long answer:

Provided that the number of values is dynamic, please try converting an array, like

my @valuesForIn  = (1,2,3,4,5); 
my $placeholders = join ',' , map {"?"} @valuesForIn;

my $query = qq~ SELECT field1
                FROM table1
                WHERE field2 IN ($placeholders) ~;

my $sth1 = $dbh->prepare($query) or die->$errstr();

$sth1->execute(@valuesForIn) or die $dbh->errstr;
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(Disclaimer: Typed into mobile, hence untested)

PS there is a fancier way to avoid the map

("?") x @valuesForIn

, but I'm not sure about the precedence here. :)

update2

please also be aware of the speed penalty of repeatedly preparing a statement for different length of lists ...