I am not sure whether the sqare brackets are part of the input. The following code works for both alternatives. It uses the fact that a hash can be created from a list by just interpreting each odd element as a key and each even element as its value.

#!/usr/bin/perl
use warnings;
use strict;

use Data::Dumper;

my $string = 'x:q,y:u,z:n';
my %hash = split /[:,]/, $string;
print Dumper \%hash;

$string = '[x:q,y:u,z:n]';
%hash = split /[:,]/, substr $string, 1, -1;
print Dumper \%hash;
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