searching a list, i always like binary search. of course, the list has to be sorted tough. here is a little script

use strict;
use warnings;

my @s = ( 'abc', 'dog', 'cat', 'rabbit', 'attic' );
my @sorted_copy = sort { $a cmp $b } @s;

print ' at:' . contains_string( 'at',  \@sorted_copy ) . "\n";
print 'cat:' . contains_string( 'cat', \@sorted_copy ) . "\n";

sub contains_string {
    my ( $var, $array ) = @_;

    return binary_string_search( $var, $array ) > -1;
}

sub binary_string_search {
    my ( $var, $array, $lo, $hi ) = @_;

    $lo = 0 unless defined $lo;
    $hi = $#{ @{$array} } unless defined $hi;

    while ( $lo <= $hi ) {

        # determine new division point
        my $mid = $lo + int( ( $hi - $lo ) / 2 );

        if ( $array->[$mid] eq $var ) {
            return $mid;
        }
        elsif ( $var le $array->[$mid] ) {
            $hi = $mid - 1;
        }
        else {
            $lo = $mid + 1;
        }        
    }

    # nothing found
    return -1;
}
[download]

i think you can achieve a speedy solution when searching a big list for more than one item.

UPDATE: minor code changes.