It "works" fine for me:

use warnings;
use strict;

use Data::Dumper;

my %d = map { $_, \&{'create_' . $_} } qw(first);

print Dumper \%d;

$d{first}->();

sub create_first {
    print "first!\n";
}
[download]

Output:

$VAR1 = {
          'first' => sub { "DUMMY" }
        };
first!
[download]

...so you need to describe what's not working as expected.

Are you wanting to call the sub like this?:

$dispatch{_create_first}->();
[download]

If so, you need to map the '_create_' to both arguments to map. This example uses a second map() to modify the $_ variable on the way into the map that creates the actual dispatch table.

use warnings;
use strict;

use Data::Dumper;

my %d  = map { $_, \&{$_} } map {'create_' . $_} qw(first);

print Dumper \%d;

$d{create_first}->();

sub create_first {
    print "first!\n";
}
[download]

Output:

$VAR1 = {
          'create_first' => sub { "DUMMY" }
        };
first!
[download]