for my $i ( 0..11 ) {
   print "yes it's a month\n" if $month eq $monthnames[$i];
}

for my $valid_months ( @monthnames ) {
   print "yes it's a month\n" if $month eq $valid_months;
}

print "Yes it's a month\n" if grep { $_ eq $month } @monthnames;

##</code><code>##

my @months = qw( jan feb mar apr may jun jul aug sep oct nov dec);
my %monthnames;
# create lookup table
$monthnames{$_}++ for @months;
print "Yes it's a month!" if exists $monthnames{$month};

##</code><code>##

$a = 1;      # set $a to 1
$a == 1;     # returns a true value if $a is numerically equal to 1
$a eq 'foo'  # returns a true value if $a is equal to the string value 'foo'

##</code><code>##

print "What, a string is numerically == 0?" if 'foo' == 0;