Create call_by_reference.pl (#737)

* Add is_palindrome.pl

Added Perl-script to find if a string is palindromic or not.

* delete is_palindrome.pl

adding subfolder

* add perl folder, create is_palindrome.pl

Perl-script for checking palindrome

* Create call_by_reference.pl

Added perl-script to show calling by reference in perl

call_by_reference/perl/call_by_reference.pl

@@ -0,0 +1,19 @@
+#!/usr/bin/perl -w
+
+my $num1 = 100;
+my $num2 = 5;
+
+sub swap{
+  $temp = $_[0];
+  $_[0] = $_[1];
+  $_[1] = $temp;
+  return;
+}
+
+print "Value of num1 BEFORE swap $num1\n";
+print "Value of num2 BEFORE swap $num2\n\n";
+
+swap($num1, $num2);
+
+print "Value of num1 AFTER swap $num1\n";
+print "Value of num2 AFTER swap $num2";