>perl -wMstrict -le
"my $orig = 'fEEfoobarFIEFooBarFoEfOoBaRfUM';
 my $mod  = 'FooBar';
 ;;
 my @chunks = split /\Q$mod\E/i, $orig, -1;
 my $new = join $mod, map lc(), @chunks;
 print qq{'$new'};
"
'feeFooBarfieFooBarfoeFooBarfum'