Please give an example (in perl code) of hose List::Util can be used to solve the OP's problem 
use warnings;
use strict;
use List::Util 'uniq';

my @given = (1,2,5,6,9,10,41..56);
my @check = (3,4,9,11,48,102);

my $c = uniq(@given);

for(@check) {
    push(@given, $_);
    print "$_ is in the list\n"
      unless $c + 1 == uniq(@given);
    pop(@given);
}

__END__

Outputs:
9 is in the list
48 is in the list

[download]
List::Util::uniq() utilizes the hash lookup referred to elsewhere in this thread.
Some efficiency is lost in this script because uniq() has to generate the hash every time it is called.
It would be more efficient if the perl code itself created the hash (just once), and then re-used that hash for each number that needs to be checked.

Perhaps anonymous had some other List::Util routine in mind.

Cheers,
Rob

In reply to Re^3: Comparing a value to a list of numbers by syphilis
in thread Comparing a value to a list of numbers by g_speran

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