Try using Perl, not C ;-)

my @array1 = qw/a b c d e f/;
my @array2 = qw/  b c d    /;
# you see: result must be a, e and f
my @in1notin2 = do {
    my %tmp = map {($_=>undef)} @array2;
    grep not exists $tmp{$_}, @array1
};
print "The elements @in1notin2 can be found in array 1, but not in arr
+ay 2\n";
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