# Access directly the last element of the array
sub queryDBI {
    my $query1 = "SELECT $_[2],$_[3],$_[-1] FROM " . $_[1];
    return $query1;
} 
print queryDBI(qw/first second third fourth fifth_and_last/),$/ x 2'

##</code><code>##

# In scalar context, @array returns the number of elements in contains.
# As @array indexes start at 0 (unless someone explicitly changes this through $[), we substract 1
sub queryDBI {
    my $query1 = "SELECT $_[2],$_[3],$_[@_-1] FROM " . $_[1];
    return $query1;
} 
print queryDBI(qw/first second third fourth fifth_and_last/),$/ x 2'

##</code><code>##

# $#array returns the index of the last element of the array.
sub queryDBI {
    my $query1 = "SELECT $_[2],$_[3],$_[$#_] FROM " . $_[1];
    return $query1;
} 
print queryDBI(qw/first second third fourth fifth_and_last/),$/ x 2'