here is a liner I use to find reverse complementary / palindromic D|RNA sequences (thought this would be up your alley because of your sig.) :

perl -nle 'tr/A-Z/a-z/;$m=length();reverse(substr($_,($m/2)+($m%2))) e
+q substr($_,0,$m/2) ? print : next'  /file/of/sequences/one_per_line
[download]

works on any list of "words" tho ... /usr/share/dict/words, etc.

update: ... this node_id has 2X \d{3} palindromes and my username is a palindrome ...