package Module1;

use strict;

use Exporter qw(import);
our @EXPORT = qw(main);

sub main {
   do_something();
}

1;

package Module2;

use strict;

use Exporter qw(import);
our @EXPORT = qw(main);

sub main {
   do_something2();
}

1;

script.pl

my $query = get_param('page') || 'main';

my %pages = (
    main => \&main, # to go to Module1 main
    another_page => \&main, #to go to Module2 main
);