Unless there's more to the hash references you're putting in @error, the hash reference itself is rather useless. That being said, you can do:

my @error =
  map $error_msg{$_},
  grep length(param($_)) >= $error_length{$_},
  @$valids;
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You can't just use $_ >= $error_length{$_}, since $_ is a field name. You need to get the value of that field, and find its length. I've done so using the CGI module.

japhy -- Perl and Regex Hacker