use DBI ':sql_types';

my $dbh = DBI->connect(...);

my $sth = $dbh->prepare("SELECT * FROM $table WHERE $field = ?");
$sth->bind_param(1, undef, SQL_VARCHAR);  # or SQL_CHAR? untested.
# For numeric types, experiment with SQL_NUMERIC or SQL_INTEGER

...
# Now go ahead, DBI will treat any data for the (first) field as a string...