Or maybe like this: 
while(my ($param, $rx) = each %laundry) {
    local $_ = $cgi->param($param)
        or die "Parameter $param not present\n";

    ($laundered_params{$param}) = /$rx/;
        or die "Invalid input for $param\n";
}

[download]
Note that both snippets will behave in probably undesired ways if any of the parameters have multiple values.

Makeshifts last the longest.

In reply to Re^2: Validating incoming CGI form data (more concise) by Aristotle
in thread Validating incoming CGI form data by Anonymous Monk

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