Select Code to Download

if ($var eq "" || $var2 eq "" || $var3 eq ""} { &complain(); }

my $var1 = $cgi->param('var1');
my $var2 = $cgi->param('var2');
...
my @list = qw(var1 var3);

foreach (@list) { if (!exists $$h{$_}) { &complain; } }