And the Once And Only Once version:

my %valid_commands = (
    jump => \&jump,

    map {
        my ($code, $cmds) = @$_;
        map { $_ => $code }, @$cmds;
    }
    [ \&go_north => [qw(north n)] ],
    [ \&go_south => [qw(south s)] ],
    [ \&go_west  => [qw(west w)] ],
    [ \&go_east  => [qw(east e)] ],
    [ \&get      => [qw(get take)] ],
    [ \&quit     => [qw(quit exit end)] ],
);
[download]

Update: removed an duplicate copy of the go_north line thanks to pfaut.

Makeshifts last the longest.