If you want to iterate through the key/value pairs of the "appLinks" hash, here's an example. Note that the OPed JSON string must be fixed before it can be decoded (misplaced commas), and also that I've added some more pairs for the example.

Win8 Strawberry 5.8.9.5 (32)  Mon 09/13/2021  6:17:03
C:\@Work\Perl\monks
>perl -Mstrict -Mwarnings

use JSON;
use Data::Dump qw(dd);

# fixed and enhanced JSON string.
my $json_string = '
[
{
            "visio": {
            "Launch": false,
            "hide": {
                "iOS": true
                         },
            "appLinks": {
                "preview_sandbox_1_link": true,
                "fooble": false,
                "wibble": 42,
                "blarfl": "darble"
            }
        }

        }
    ]
';
# print "$json_string \n";  # for debug

my $arrayref = decode_json $json_string;
# dd $arrayref;  # for debug

# convenience variable.
my $appLinks_hashref = $arrayref->[0]{'visio'}{'appLinks'};

for my $appLink_key (keys %{ $appLinks_hashref }) {
    print "appLink key '$appLink_key' -> ";
    print "appLink value '$appLinks_hashref->{$appLink_key}' \n";
    }

^Z
appLink key 'wibble' -> appLink value '42'
appLink key 'blarfl' -> appLink value 'darble'
appLink key 'preview_sandbox_1_link' -> appLink value 'true'
appLink key 'fooble' -> appLink value 'false'
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