use CGI;
my $q = new CGI qw(param);
print "\$q->param($_) = " . $q->param($_) . "\n" for $q->param;
print param('asdf');  # not imported, error
__END__

prints:
$ perl test.pl
$q->param(keywords) = param
Undefined subroutine &main::param called at - line 4.