use strict;
use warnings;

use Data::Dumper;

my @arr1 = ('a');
my $var1 = 'b';

my (@surprise) = grep($var1, @arr1);

print Dumper( \@surprise );

##</code><code>##

use strict;
use warnings;

my @arr2 =('a', 'b');
my @arr1 = ('a');

my %reference = map { $_ => 1 } @arr1;

for my $var1 (@arr2) {
    print "match $var1\n"
        if exists $reference{$var1};
}