Thanks all, many great ideas which I've percolated into my final solution.
If you see any problems, please drop a post :)
I chose to instead of checking the perl variables, check the CGI parameters - which made much more sense, thanks for the ideas Monks;

my @varlist = qw(var1 var2 var3);

foreach (@varlist) {
    if (!defined $cgi->param($_) || $cgi->param($_) eq "") {
        &complain($_);
        }
    }
[download]

Where &complain() can translate var# into the HTML side field name (ie. "Phone number", instead of 'phone').

Cheers all;
JP,
-- Alexander Widdlemouse undid his bellybutton and his bum dropped off --