my ($name) =          (param('name')         ||'') =~ /^([[:alpha:][:punct:][:space:]]+)$/;
my ($color) =         (param('color')        ||'') =~ /^([[:alpha:]]+)$/;
my ($otherReqParam) = (param('otherReqParam')||'') =~ /^([[:alpha:]]+)$/;

#deal with all other params in a similar fashion.
print 'location: http:/www.somesite.com/error.htm', $/, $/
     unless defined $name
     and    defined $color
     and    defined $otherReqParam;
     
# If we got here we have everything we need, untainted.
...