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