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+#!/usr/bin/env perl
+
+# Task 1: Duplicate Removals
+# Submitted by: Mohammad Sajid Anwar
+# 
+# You are given a string, $str, consisting of lowercase English letters.
+# 
+# Write a script to return the final string after all duplicate removals have been made. Repeat duplicate removals on the given string until we no longer can.
+# 
+# A duplicate removal consists of choosing two adjacent and equal letters and removing them.
+# 
+# Example 1
+# Input: $str = 'abbaca'
+# Output: 'ca'
+# 
+# Step 1: Remove 'bb' => 'aaca'
+# Step 2: Remove 'aa' => 'ca'
+# 
+# Example 2
+# Input: $str = 'azxxzy'
+# Output: 'ay'
+# 
+# Step 1: Remove 'xx' => 'azzy'
+# Step 2: Remove 'zz' => 'ay'
+# 
+# Example 3
+# Input: $str = 'aaaaaaaa'
+# Output: ''
+# 
+# Step 1: Remove 'aa' => 'aaaaaa'
+# Step 2: Remove 'aa' => 'aaaa'
+# Step 3: Remove 'aa' => 'aa'
+# Step 4: Remove 'aa' => ''
+# 
+# Example 4
+# Input: $str = 'aabccba'
+# Output: 'a'
+# 
+# Step 1: Remove 'aa' => 'bccba'
+# Step 2: Remove 'cc' => 'bba'
+# Step 3: Remove 'bb' => 'a'
+# 
+# Example 5
+# Input: $str = 'abcddcba'
+# Output: ''
+# 
+# Step 1: Remove 'dd' => 'abccba'
+# Step 2: Remove 'cc' => 'abba'
+# Step 3: Remove 'bb' => 'aa'
+# Step 4: Remove 'aa' => ''
+
+use strict;
+use warnings;
+
+my $str = 'abbaca';
+get_noduplicate($str);
+
+$str = 'azxxzy';
+get_noduplicate($str);
+
+$str = 'aaaaaaaa';
+get_noduplicate($str);
+
+$str = 'aabccba';
+get_noduplicate($str);
+
+$str = 'abcddcba';
+get_noduplicate($str);
+
+exit 0;
+
+sub get_noduplicate {
+    my $str_orig = shift;
+    my $str = $str_orig;
+
+    do {
+        $str =~ s/(\w)\1//;
+        
+    } while $str =~ /(\w)\1/;
+
+    printf "'%s' -> '%s'\n", $str_orig, $str;
+}