I'd recommend against doing this:

$query->textfield(
  -name      => 'BillName',
  -value     => $query->param('BillName'),
  -maxlength => 70,
  -size      => 50,
)
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If there is no parameter named BillName then param('BillName') will return; without a value, which causes the hash to have this structure:

$query->textfield(
  -name      => 'BillName',
  -value     => -maxlength,
  70         => -size,
  50         => undef,
)
[download]

You can confirm with this example code:

#!/usr/bin/perl
use strict;
use warnings;
use CGI;
use Data::Dumper;

my $cgi = CGI->new;

my %data = (
  a => $cgi->param('a'),
  b => $cgi->param('b'),
);

print "Content-type: text/plain\n\n";
print Dumper(\%data);
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