my $str='xjxexrxoxexnxexsxxx';
my $idx = -1;
my $str_2nd = '';
 
$str_2nd .= substr( $str, $idx+=2, 1) while( $idx < length $str);
 
print "\n$str_2nd\n";

##</code><code>##

my $str='xjxexrxoxexnxexsxxx';
 
my @chars = split //, $str;
my @chars_2nd;

while ( scalar @chars ){
  shift @chars;
  push @chars_2nd, shift @chars;
}
 
print join '', @chars_2nd;