$username = sanitize(
  data        => param('username'), # call from CGI form
  field       => 'Username', # field name
  obligatory  => 1, # field is obligatory
  min         => 8,
  max         => 8,
  regex       => '%;&()#\w ', # customised regex
);

sub sanitize {
  # date, field, obligatory, min, max, numeric, regex

  my %checks = @_;
  $checks{'data'} =~ s/\s+/ /g;
  # remove leading and trailing blanks
  $checks{'data'} =~ s/^\s+//;
  $checks{'data'} =~ s/\s+$//;

  # Default regex
  my $default = '-\@\w. ';
  $checks{'regex'} = $checks{'regex'} ? $checks{'regex'} : $default;
   
  # This part changed by graff
  my $length = length($checks{'data'});
  if (!$length) { # empty string
    if ($checks{'obligatory'}) {
      bail_out("$checks{'field'} is obligatory");
    } else {
      return;
    }
  }
  if ($checks{'data'} =~ /([^$checks{'regex'}])/) {
    bail_out("Bad input.");
  }
  if ($checks{'numeric'} and $checks{'data'} =~ /[^\d]/) {
    bail_out("Non-numeric character(s) in numeric field");
  }
  if ($checks{'min'} and $length < $checks{'min'}) {
    bail_out("Too long.");
  }
  if ($checks{'max'} and $length > $checks{'max'}) {
    bail_out("Too short");
  }
  return $checks{'data'};
}
[download]