package something;
@something::ISA=qw(basePack);

sub todo
{
    #something::todo code in here
}

package diffrent;
@diffrent::ISA=qw(basePack);
sub todo
{
    #diffrent::todo code in here
}

package basePack
sub new
{  
    return bless({},shift);
}
sub act
{
    my $self=shift;
    $self->todo(@_);
}

#package main.
#!/perl
use strict;
use lib qw(/path/to /another/pathto);
use diffrent;
use something;

my $something=new something;
my $diffrent = new diffrent;
$something->act($arg1, $arg2);  #something::todo;
$diffrent->act($arg3,$arg4);    #diffrent::todo;