perl - How do I find which elements in one array aren't in another?

Question

I am new to programming and hence I am stuck on a basic level problem.

Following is code I wrote for comparison. But the result I get does not make sense to me. I would appreciate if someone could tell me what is going wrong.

There are two arrays: @array1 , @array2 of unequal length.

I wish to compare both and list down values not present in @array1.

my %temp = map {$_,$_}@array2;
for (@array1){
next if exists $temp{$_};
open (FILE, ">>/filename") or die "$!";
print FILE "$_
";
close(FILE);
}

Answer 1

See the FAQ How do I compute the difference of two arrays? How do I compute the intersection of two arrays?

Adapting the code you posted:

#!/usr/bin/perl

use strict; use warnings;

my @x = 1 .. 10;
my @y = grep { $_ % 2 } @x;

my %lookup = map { $_ => undef } @y;

for my $x ( @x ) {
    next if exists $lookup{$x};
    print "$x
";
}