my $foo;
my $bar;
my @args;

# Get $foo $bar and @args somewhere around here...

my %despatch_table = ("one" => ( "alpha" => \&func_onealpha,
                                 "beta"  => \&func_onebeta),
                      "two" => ("alpha"  => \&func_twoalpha,
                                "beta"   => \&func_twobeta));

my $answer;

if ($answer = &${$despatch_table{$foo}}{bar}(@args))
{
    # Do something with $answer
}
else
{
    # Bad values throw an error
}


sub func_onealpha
{
    # Do stuff here
}

sub func_onebeta
{
    # Do stuff here
}

sub func_twoalpha
{
    # Do stuff here
}

sub func_twobeta
{
    # Do stuff here
}