In the example code below, assuming that the value $keyvalue is constantly changing, I am attempting to use a single line (or something similarly contained) to test and see if the current $keyvalue already exists. If it does, then do nothing. If it does not, then push it. This line would reside within a while statement which is why it needs to be contained within a few lines.

Preserving order does not matter as long as there are no duplicate values.

my $key = "numbers";
my $keyvalue = 1;

my %hash = ($key => '1');

push (@{$hash{$key}}, $keyvalue) unless exists $hash{$key};

I am not getting any errors with use strict; use warnings;, but at the same time this is not working. In the example above, I would expect that since the default value is 1 that the $keyvalue would not be pushed as it is also 1. Perhaps I have gotten myself all turned around...

Are there adjustments to get this to work or any alternatives that can be used instead to accomplish the same thing?