Short answer: you need to escape the backslash.

Long answer: Never shell out from perl to run awk (see Hippo's Law of Perl). Instead do something like this:

($UUID) = map { (split (/"/, $_))[-1] } grep { /IOPlatformUUID/ } `ior
+eg -d2 -c IOPlatformExpertDevice`;
print $UUID;
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Untested, because I don't have ioreg installed here but you should hopefully get the gist. Equivalent SSCCE:

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

my ($UUID) = map { (split (/"/, $_))[-1] } grep { /IOPlatformUUID/ } '
+IOPlatformUUID = "foo"';
print "$UUID\n";
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