jwlarson3rd has asked for the wisdom of the Perl Monks concerning the following question: 

my $name= $p->param('name')||'';
if ($name =~ /^([a-zA-Z0-9]+)$/) {
        $name = $1;                     # $data now untainted
    }

[download]
I need some help with regular expressions. I would like to restrict $name to large and small case letters and numbers. john larson

Replies are listed 'Best First'.
Re: validating form input
by leira (Monk) on Feb 25, 2004 at 04:03 UTC
    What do you mean by "restrict"? Do you want to replace characters that aren't alphanumeric with something else? Do you simply want to know if the string contains non-alphanumeric characters, so that you can act appropriately?

    Linda

[reply]
      I would like to delete everything but large and small case letters and numbers john larson
[reply]
        How about this? 

        # replace non alphanumeric characters with ''
$name =~ s/\W//g;

# replace '_' with '' because \W doesn't catch those
$name =~ s/_//g;

        [download]

        Linda

[reply]
[d/l]
        perl -e "my $t = \"ABC def 123*GHI;?. jk\"; $t =~ s/([^A-Z0-9 ])*//ig;
+ print $t;## don't accept any char. except... _______^"

        [download]
        ...

        ABC def 123GHI jk

[reply]
[d/l]

        You want the tr (transliteration) operator:

        $name =~ tr/A-Za-z0-9//cd;

         --
        LP^>

[reply]
[d/l]
[select]
Re: validating form input
by chimni (Pilgrim) on Feb 25, 2004 at 04:26 UTC

    you could do something like this if you wanted to restrict a field to a certain set.
    The @wrong array will contain all violating enteries (if you want them in your error msg. 
    my $test="%%6ffgg";
die("illegal character found".join(',',@wrong)."\n") if @wrong = $test
+ =~(m/([^a-zA-Z0-9])/g);

output
illegal character found%,%

    [download]

    HTH
[reply]
[d/l]

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