File Uploading

#!/usr/bin/perl
# file: sequpload.pl

use CGI ':standard';

print header;
print start_html('Reverse Complementation'),
  h1('Reverse Complementator'),
  start_multipart_form,
  "Enter your sequence here:",br,
  textarea(-name=>'sequence',-rows=>5,-cols=>60),br,
  'Or upload a sequence here: ',filefield(-name=>'uploaded_sequence'),
  submit('Reverse Complement'),
  end_form,
  hr;

if ( param ) {

  my $sequence;

  # look for the uploaded sequence first...
  if ( my $upload = param('uploaded_sequence') ) {
    print h2("Reverse complement of $upload");

    while (my $line = <$upload>) {
      chomp $line;
      next unless $line =~ /^[gatcnGATCN]/;
      $sequence .= $line;
    }

  } else { # ... not found, so read it from the text field
    print h2('Reverse complement');
    $sequence = param('sequence');
  }

  $reversec = do_reverse($sequence);
  $reversec    =~ s/(.{60})/$1\n/g;  # do word wrap
  print pre($reversec);
}

print end_html;

sub do_reverse {
  my $seq = shift;
  $seq =~ s/\s//g;               # strip whitespace
  $seq =~ tr/gatcGATC/ctagCTAG/; # complement
  $seq = reverse $seq;           # and reverse
  return $seq;
}