If you really want to split into records with a regex:

But I don't know why you want the records at all. This format seems easiest to parse line-by-line.

my @essids;
for (qx| sudo iw dev wlan0 scan |) {
   /^\s*SSID:\s*(.*)/ and push @essids, $1;
}
[download]

If you need other information besides the ssid, maybe you can just do something like this:

my @records;
for (qx| sudo iw dev wlan0 scan |) {
  if (/^BSS\s*(.*)/) { push @records, { BSS=>$1 } }
  elsif (/^\s*(\w+):\s*(.*)/) { $records[-1]{$1} = $2 if @records }
}
foreach my $record (@records) {
  print "$record->{SSID}\n";
}
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