The following code is part of a CGI.pm and HTML::Template script I'm working on.   It receives and untaints browser-supplied CGI param, then compares with directory listing of URLlist files, and serves content accordingly.   Amazingly enough, it actually works.   {grin}

Two questions:
1 - How to add site home (index.pl?page=home) as the default if *no* param given, but still fail if *bad* param given?
2 - Untainting regexp that will reject if non-word character anywhere in provided param, not just if non-word char is first character.

All suggestions welcome and appreciated.
    cheers,
    Don
    striving for Perl Adept
    (it's pronounced "why-bick")

  

# Read in URL file query and untaint
# one or more word characters
if ($query = param('page') =~ /(\w+)/) {
    $urlist = $1;
    }
else {die "Please request pages by alphanumeric name only.
    You might find what you're looking for by starting at site
    home of http://host.dom/index.pl?page=home\n";
    }


# Build array of urlist files
# Confirm that supplied param is valid file
opendir DIR, "$confdir/";
my @files = grep {
    $_ ne '.' &&
    $_ ne '..' &&
    }
readdir DIR;
closedir DIR;
unless (grep{$_ eq $urlist} @files) {
    die "You requested a page that does not exist.
    You might find what you're looking for by starting at site
    home of http://host.dom/index.pl?page=home\n";
    }


# read lists of page URLs from external file
# loop through lists, parsing for HTML::Template use
unless (my $return = do "$confdir/$urlist") {
    die "Cannot parse $urlist: $@" if $@;
    die "Cannot do $urlist: $!"    unless defined $return;
    die "Cannot run $urlist"       unless $return;
    }
for (my $i = 0; $i < $#url_array; $i+=2) {
    my($loop, $aref) = @url_array[$i, $i+1];
    my @vars;
    for (my $j = 0; $j < $#{$aref}; $j+=2) {
        my($name, $url) = @{$aref}[$j, $j+1];
        push @vars, { name => $name, url => $url };
        }
    $template->param($loop, [ @vars ]);
    }

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In reply to Default CGI.pm param() if none provided? by ybiC

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