$ cat test.pl
  #!/usr/bin/perl

  use warnings;
  use strict;

  use CGI;
  use Data::Dumper;

  my $q = CGI->new;

  my %h = (
      one => $q->param('one'),
      two => $q->param('two')
  );

  print Dumper \%h;
  __END__

$ perl test.pl
$VAR1 = {
          'one' => 'two'
        };

$ perl test.pl one=1
Odd number of elements in hash assignment at test.pl line 11.
$VAR1 = {
          'one' => '1',
          'two' => undef
        };

$ perl test.pl two=2
Odd number of elements in hash assignment at test.pl line 11.
$VAR1 = {
          'one' => 'two',
          '2' => undef
        };

$ perl test.pl one=1 two=2
$VAR1 = {
          'one' => '1',
          'two' => '2'
        };