Takes two arguments, a ref to a CGI object (or anything that implements param with the same semantics as CGI) and a ref to a hash of (key, valitation) pairs.

sub validate_data($$)
{
    my $q = shift;
    my $tmpl = shift;

    my %data = ();
    my %invalid = ();

    foreach my $key (keys %{$tmpl})
    {
        my $value = $q->param($key);
        if (&{$tmpl->{$key}}($value))
        {
            $data{$key} = $value if defined $value;
        } else {
            $invalid{$key} = 1;
        }
    }

    return (\%data, \%invalid);
}
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And the validation routines are:

sub is_string
{
    return sub {
        return $_[0] ne "";
    };
}

sub is_number
{
    return sub {
        return $_[0] =~ m{^\d+$};
    };
}

sub is_range($$)
{
    (my $l, my $u) = @_;
    return sub {
        return $_[0] =~ m{^\d+$} && $_[0] >= $l && $_[0] <= $u;
    };
}

sub is_in_list($)
{
    my $l = shift;
    return sub {
        return (grep { $_[0] eq $_ } @{$l}) != 0;
    };
}

sub is_email
{
    return sub {
        return $_[0] =~ m{^[-.+a-z0-9]+\@[-.+a-z0-9]+$}i;
    };
}

sub is_required
{
    my $t = shift;
    return sub {
        defined $_[0] and &{$t}($_[0]);
    };
}

sub is_optional
{
    my $t = shift;
    return sub {
        return defined $_[0] ? &{$t}($_[0]) : 1;
    };
}

sub is_equal
{
    my $v = shift;
    return sub {
        $_[0] eq $v ? 1 : 0;
    }
}
[download]

The "is_equal" routine probably needs to be generalized to be able to compare numbers and other things... You can use it like this:

my %fields = (
  name => is_required(is_string()),
  email => is_required(is_email()),
  phone => is_optional(is_phone()),
);
[download]