It doesn't exist in the example, which is only creating the INSERT statements, presumably to pipe into, e.g., the mysql command line client:

mysql -u user -p < inserts.sql

If the $dbh were in the example, then:

(a) you could avoid that (eek!) archaic escapeSingleQuote() sub, e.g., my $released = $dbh->quote($released), but much better:

(b) as mentioned, use the SQL placeholders to avoid quoting altogether, but

(c) if you really want to print the INSERT's, just do method (a). Start by declaring the $dbh, e.g. for MySQL:

my $dbh = DBI->new( 'DBI:mysql:my_db', 'db_user', 'db_pass');