#!/usr/bin/perl
use warnings;
use strict;

my $a="toto-titi-1.2-2mdk.xxx.rpm";
print "$a\n" ;
my @b = split(/-/,$a);
print join('-',@b[0 .. $#b -2]), "\n";

 $ perl /tmp/e.pl
toto-titi-1.2-2mdk.xxx.rpm
toto-titi