use warnings;
use strict;
use List::MoreUtils qw (any);

my $var = 3;

if (grep { $var == $_ } 2, 3) {
    print "in list\n";
}
else {
    print "not in list\n";
}

if (any { $var == $_ } 2, 3) {
    print "in list\n";
}
else {
    print "not in list\n";
}

my %vals = map {$_ => 1} 2, 3;
if (exists $vals{$var}) {
    print "in list\n";
}
else {
    print "not in list\n";
}

__END__

in list
in list
in list