it's worse than obfustication, it's out right betrayal worthy of the machiavellian-est of perl programers. if param('color') returns a false value (be it undef or the empty string) the regex against '' is going to always return undef.

I assume you simply want to provide a default value for $color if a) it's not present (param('color') returns empty string or undef) or b) it isn't a sequence of only [:alpha:] chars.

use locale;

my $color = param('color') =~ /^\w+$/ ?
            param('color') :
            "default color";
[download]

my $color = "default color";
$color = param('color') if param('color') =~ /^\w+$/;
[download]

of course, the real solution to this is:

use locale;

sub is_alpha {
  my ($datum) = @_;
  # return "" so we don't get unitialized value errors
  $datum =~ /^(?:\w+)$/ ? $datum : "";
}

my $color = is_alpha(param('color')) || "default value";
[download]

Or why not sub class CGI and add these checks to CGI::param? Have MyCGI::param return an object with color, name, etc methods so you could just write $cgi->param->color;