package foo;

BEGIN {
    use Exporter;
    our(@ISA, @EXPORT); # use vars has been depreciated
    @ISA = qw(Exporter);
    @EXPORT = qw(header);
}

sub header {
    use CGI;
    # using OO-syntax for CGI.pm allows you the greatest flexibility
    my $cgi = new CGI;
    return $cgi->header;
}

1;