use 5.010;
my $string = "abcFOOdefghFOOiFOOjklmFOOnopqrFOOstuvFOOwxyz";
my @portions = split /FOO/, $string, -1;
shift @portions;
pop @portions;
say "Lengths are:";
say $_ for map { sprintf("%d ('%s')", length, $_) } @portions;