Per OP Update: I have an array Say, @array1 = qw (1,1,1,2,3,4,4,4,5,6,1,1,1,1,...). From this array i have to extract an output as "1,1,1,2,3,4,4,4,5,6,1" (i.e. to remove the X-number of 1's with just 1).

One way:

c:\@Work\Perl\monks>perl -wMstrict -MData::Dump -le
"my @ra = (1, 1, 1, 2, 3, 4, 4, 4, 5, 6, 1, 1, 1);
 dd \@ra;
 ;;
 my $one;
 $one = pop @ra while $ra[-1] == 1;
 push @ra, $one if defined $one;
 dd \@ra;
"
[1, 1, 1 .. 4, 4, 4, 5, 6, 1, 1, 1]

[1, 1, 1 .. 4, 4, 4, 5, 6, 1]
[download]

Update: Another way:

c:\@Work\Perl\monks>perl -wMstrict -MData::Dump -le
"my @ra = (1, 1, 1, 2, 3, 4, 4, 4, 5, 6, 1, 1, 1);
 dd \@ra;
 ;;
 my $highest;
 for my $i (reverse 0 .. $#ra) {
   last if $ra[$i] != 1;
   $highest = $i;
   }
 $#ra = $highest if defined $highest;
 dd \@ra;
"
[1, 1, 1 .. 4, 4, 4, 5, 6, 1, 1, 1]

[1, 1, 1 .. 4, 4, 4, 5, 6, 1]
[download]

Upon reflection, I think the second approach is better: it's more flexible. If one wanted to trim all but one undef value from the end of an array, one need only change the test within the for-loop from
    last if $ra[$i] != 1;
to
    last if defined $ra[$i];
and the job's done. The first approach does not have this flexibility.