my $do = 1;
for (0...9) {
    stuff_to_do_always();
    if ($do) {
        stuff_to_do_first_time();
    }
    else {
        stuff_to_do_other_times();
    }
    $do = 0;
}
##</code><code>##

use DBI;
my $dbh = DBI->connect("DBI:mysql:database=chess", "usr", "pwd");  # or whatever

my @line;
my $sth;
while (<DATA>) {
# your parsing:
    chomp;
    next if /^\s*$/;
    @line = split /;/;
# these lines deal with the only variation in 
# your data I can see - there may be others:
    if (@line == 3) {
        push @line, $line[2];
        $line[2] = 'NULL';
    }
# and finally, DBI takes the strain:
    $sth = $dbh->prepare("INSERT INTO eco_class (eco_id,eco,opening,variation,moves) VALUES (NULL,?,?,?,?)") or die $dbh->errstr;
    $sth->execute(@line) or die $dbh->errstr;
}