If memory really is a problem (and I doubt it from the numbers you gave), you can could use 

for (0..$#line2) {
   my $i = $line2[$_];
   for (0..$#line1) {
      my $j = $line1[$_];
      print $i if if $i eq $j;
   }
}

[download]

If memory isn't a problem, you can use a much faster solution: 

my %lookup;
++$lookup{$_} for @line2;

for (@line1) {
   print if $lookup{$_};
}

[download]

Finally, you might want to get rid of duplicate messages. 

my %lookup;
$lookup{$_} = -1 for @line2;

for (@line1) {
   print if !++$lookup{$_};
}

[download]

In reply to Re: Iterating through Two Arrays. Is there a better use of memory? by ikegami
in thread Iterating through Two Arrays. Is there a better use of memory? by Jeri

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