I prefer to use Set::Scalar for this type of condition.

use strict;
use Set::Scalar;

my @testItems = qw|a b c d e f g|;
my $set = Set::Scalar->new('a', 'b', 'c');

foreach my $item (@testItems)
  {
    if($set->has($item))
       {
         print "$item is in set\n";
       }
  }
__END__
Results:
a is in set
b is in set
c is in set
[download]

Although I haven't looked at the performance of this package compared to methods suggested in this thread.