#!/usr/bin/perl use strict; use warnings; $_=<<'.'; bEjhMELGUaL smtMDEYSxyDvuQiUfAbJfYMPnfJAqaPnKL VWZWSdfYRSaSGlXOyPfxusC dtRAHabcdecgf taNdvtKdBlJcnFryVXObEDvawRyviWO hwlKiBpDWYeBPYhlpKFvrSeQ ksWmkXqQdLQPIzvKFE Jqrclq mPqQbMvkAx LtVuFMehKirSATuqlFzqwRknocsrcKXAE FNbOivdvkRonEkg apuPyHpTlssvVs BbwiHBvhfrSFwVkhwHkvoYjaGgntzFbEvPCIttD IAlYqoLUjtxsYvbwUBHIoMYmPJbGeXymuwERkHwSyKbE XMCcFgsYPzmJbVUsOwfDTgUiJ . while (/(?=([a-zA-Z]{8}))/g) { my @l = (my $found=$1) =~ /./g; print $found, "\n" if $l[2] eq $l[5] and do { my %h; @h{@l}=(); 7 == keys %h; } } __END__