#!/usr/bin/perl

use strict;
use warnings 'all';

# Given an array and a value, move all elements equal to the
# value one position to the left - do a block move if there
# are consecutive elements of the value.
 
my @array = (18, 18, 13, 27, 4, 18, 12, 6, 7, 18, 18, 18, 14, 15);        
my $value =  18;
 
print "@array\n";
@array [do {my $l; reverse map {
               $value eq $array [$_] ? do {$l = $_ unless defined $l; $_ - 1}
                                     : do {$_ = $l if defined $l; undef $l; $_}
               } reverse 0 .. $#array}] = @array;          
print "@array\n";
__END__
18 18 13 27 4 18 12 6 7 18 18 18 14 15
18 18 13 27 18 4 12 6 18 18 18 7 14 15