It's a palindrome if

str[0] eq str[str_length-1] and
str[1] eq str[str_length-2] and
str[2] eq str[str_length-3] and
...
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Or, it's not a palindrome if

str[0] ne str[str_length-1] or
str[1] ne str[str_length-2] or
str[2] ne str[str_length-3] or
...
[download]