Okay. Try:

use Data::Dump qw[ pp ];

my @v = ([100, 200],[200, 300],[200, 100]);;

my %uniq; 
my @r = grep{ 
    ++$uniq{ join $;, $_->[0], $_->[1] } == 1 
    and 
    ++$uniq{ join $;, $_->[1], $_->[0] } == 1 
} @v;;

pp @r;;
([100, 200], [200, 300])
[download]

This is nice but it misses the case where the pair of numbers is equal, as the first test will pass, but the second will fail. I believe this small modification will cover that case though

use Data::Dump qw[ pp ];

my @v = ([100, 200],[200, 300],[200, 100], [200, 200]);;

my %uniq; 
my @r = grep{
    ++$uniq{ join $;, sort @$_ } == 1 
} @v;;

pp @r;;
#([100, 200], [200, 300], [200, 200])
[download]

- Miller

I am sorry..i am getting following error message:

Can't locate Data/Dump.pm in @INC (@INC contains: /etc/perl /usr/local/lib/perl/5.10.1 /usr/local/share/perl/5.10.1 /usr/lib/perl5 /usr/share/perl5 /usr/lib/perl/5.10 /usr/share/perl/5.10 /usr/local/lib/site_perl /usr/local/lib/perl/5.10.0 /usr/local/share/perl/5.10.0 .) at test.pl line 1. BEGIN failed--compilation aborted at test.pl line 1.

The code is very high level to people like me..if you would not mind, could you comment it please..

Data::Dump is just to dump out the array, so you could see, that the function does what you want. You could omit using it and pp-line too.

AFIU grep here triggers counters, so it can throw away pairs already seen.

Browser: Once again, your solution is a thing of beauty. I bow to your perliness.