my $_name = param('name');
my ($name) = $_name =~ /^([[:alpha:]]+)$/ if defined $_name;
my $_color = param('color');
my ($color) = $_color =~ /^([[:alpha:]]+)$/ if defined $_color;
my $_otherReqParam = param('otherReqParam');
my ($otherReqParam) = $_otherReqParam =~ /^([[:alpha:]]+)$/ if defined $_otherReqParam;
# ... and so on for all the other params, and then
print 'location: http:/www.somesite.com/error.htm', $/, $/
     unless defined $name
     and    defined $color
     and    defined $otherReqParameter;
....