It's kind of ugly, but it might be the best solution..

It is ugly and it most definitely is not the best solution.

The correct solution involves using a hash and iterating through that hash. One way of doing this could be:

my @varnames = qw(
    Var1
    Var2
    Var3
);

my %params;
@params{@varnames} = map { $cgi->param($_) } @varnames;

if (grep { !defined $params{$_} || $params{$_} eq '' } @varnames)
{
    &complain;
}

# Now, at this point, you have read in all your parameters
# and verified that each is defined as well as not the
# empty string.

# Do other stuff here.
[download]

This also illustrates a very important concept in application development - separating the things that can change from the things that won't ... aka Encapsulation. We are separating out the logic from the things being logic'ed. This is especially important for you because you don't know which varnames you want to apply this logic to.

------
We are the carpenters and bricklayers of the Information Age.

Don't go borrowing trouble. For programmers, this means Worry only about what you need to implement.

Please remember that I'm crufty and crochety. All opinions are purely mine and all code is untested, unless otherwise specified.