# this part is just so you don't get an "requires explicit
# declaration" error
my @lines = getLines();
my @angel = getAngel();
my @a;my @b;
# ok...here's some magic
# we create a hash whose keys come from @lines. Why
# do this? Since checking an element in a hash is O(1)
# it is much faster than searching the array @lines
# ...also, on a side node the map is so we do case
# insensitive checking when we look for exists
my %hash;
@hash{map(lc,@lines)} = ();

# ok, now we create a loop that will set $_ to the numbers
# from 0 to $#angel. We could also do for (@angels) to get
# the actual values, but since you pushed the index of
# matches into @a and @b, I opted for this option instead.
for (0..$#angel) {
# ok, since we didn't actually set each hash element to any
# value, we can't compare it against anything...BUT, we can
# check to see whether or not it exists
  if (exists $hash{lc($angel[$_])}) {
     # hey, we have a match, take care of it
  } else {
     # darn...not a match :-/
  }
}