If you run to more than two conditions, you can use a mapping hash

use strict;
use warnings;

# the simple case, as requested
my $rain = int rand 2;
my %rain_map = (
    0 => 'dry',
    1 => 'wet',
);
my %Weather = ( precipitation => $rain_map{$rain} );
print "Simple weather($rain) is $Weather{precipitation}\n";

# a little more
my $precip = int rand 5;
my %precip_map = (
    0 => 'dry',
    1 => 'wet fog',
    2 => 'wet rain',
    3 => 'wet hail',
    4 => 'plague of locusts',
);

my %More_Weather = ( precipitation => $precip_map{$precip} );
print "More weather($precip) is $More_Weather{precipitation}\n";
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Cheers,
R.