BASH Palindrome Checker

Question

This is my first time posting on here so bear with me please.

I received a bash assignment but my professor is completely unhelpful and so are his notes.

Our assig

Answer 1

Another solution that uses a Perl-compatible regular expressions (PCRE) with recursion, heavily inspired by this answer:

grep -P '^(?:([a-z])(?=[a-z]*(\1(?(2)\2))$))++[a-z]?\2?$' /usr/share/dict/words