perl -le "for($ARGV[0]=~/\-/g){my@a;map{$a[$_]++for(eval s/\-/\.\./r)}
+map{s/^([^,]*),?//;$1}@ARGV;print+(join'-',(grep$a[$_]==2,0..$#a)[0,-
+1])}"    
 
"25-40,74-93,95-120,130-149"     "31-47,84-99,107-123,137-151"

31-40
84-93
107-120
137-149
[download]

L*

PS this should be the sub to add to the above bench ( UPDATE it had many errors: corrected)

sub _oneliner{
        my @res;
        for($TM_part1=~/\-/g) { 
            my @arr;

            # map{ $arr[$_]++ for (eval s/\-/\.\./r) } map{ s/^([^,]*)
+,?//; $1 }$TM_part1, $TM_part2;
            # semplified a bit, see below

            map{s/^([^,]*),?//;$arr[$_]++ for( eval $1 =~ s/\-/\.\./r 
+)}$TM_part1,$TM_part2;
            push @res,(join'-',(grep { defined $arr[$_] and $arr[$_] =
+= 2 }0..$#arr)[0,-1] );
        }
        return join ',', @res;
}


__END__
1..4
ok 1
ok 2
ok 3
ok 4
               Rate     Span     Perl     Pair Oneliner
Span        12055/s       --     -27%     -84%    -100%
Perl        16553/s      37%       --     -79%    -100%
Pair        77602/s     544%     369%       --     -99%
Oneliner 11429533/s   94715%   68949%   14628%       --
[download]

UPDATE the double map is really redundant and unneeded in the above sub:

# map{$arr[$_]++ for(eval s/\-/\.\./r)}map{s/^([^,]*),?//;$1}$TM_part1
+,$TM_part2;
# should be:
    
map{s/^([^,]*),?//;$arr[$_]++ for( eval $1 =~ s/\-/\.\./r )}$TM_part1,
+$TM_part2;

# so also the oneliner can be reduced:

perl -le "for($ARGV[0]=~/\-/g){my@a;map{s/^([^,]*),?//;$a[$_]++for eva
+l$1=~s/\-/\.\./r}@ARGV;print join'-',(grep$a[$_]==2,0..$#a)[0,-1]}"
        "25-40,74-93,95-120,130-149"     "31-47,84-99,107-123,137-151"

31-40
84-93
107-120
137-149
[download]

PS I fixed 1..$#a with 0..$#a in the above code snippets