You might want to investige import and export capabilities of your DBMSs for example, if Ingres can dump to CSV, MySQL can easily import it with the LOAD command.

If you go the manual method, you can use something like this:

my $ingres_dbh  = DBI->connect( @ingres_connection_args );
my $mysql_dbh   = DBI->connect( @mysql_connection_args  );
my @sql = (
    { select => 'SELECT f1,f2,f3 FROM master_table_1'
    , insert => 'INSERT INTO back_table_2(f1,f2,f3) VALUES(?,?,?)'
    }
    ,
    { select => 'SELECT abc1,abc2,abc3 FROM master_table_2'
    , insert => 'INSERT INTO back_table_2(abc1,abc2,abc3) VALUES(?,?,?
+)'
    }
);
for( 0..1 ){
    my $select = $ingres_dbh->prepare( $sql[$_]->{select} );
    my $insert = $mysql_dbh->prepare(  $sql[$_]->{insert} );,
    while(my $row = $select->fetch){
        $insert->execute(@$row);
    }
}
[download]