my $sql = <<EOSQL;

SELECT  something 
FROM    atable 
WHERE   data IN (?)

EOSQL

##</code><code>##

my $sql = <<EOSQL;

SELECT  something 
FROM    atable 
WHERE   data IN (@{[join ',', ('?') x $size]})

EOSQL

##</code><code>##

my $sql = do {
    my @holders = ('?') x $size;
    local $" = ',';
    <<EOSQL;

SELECT  something 
FROM    atable 
WHERE   data IN (@holders)

EOSQL
};

##</code><code>##

my $sql = sprintf <<EOSQL, join ',', ('?') x $size;

SELECT  something 
FROM    atable 
WHERE   data IN (%s)

EOSQL