use locale;

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

##</code><code>##

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

##</code><code>##

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";