For this particular example,  no strict 'refs'; seems to be essential. (Checked under both ActiveState 5.8.9 and Strawberry 5.14.4.1)

  
c:\@Work\Perl\monks>perl -wMstrict -MData::Dump -le
"my %res;
 ;;
 no warnings qw(uninitialized);
 ;;
 @{$res{'act'}} = sort {
   return 0 unless $a->{'act'} =~ /^move/ and $b->{'act'} =~ /^move/;
   return $a->{'act'} cmp $b->{'act'};
   } @{$res{'acts'}};
 dd \%res;
"
Can't use an undefined value as an ARRAY reference at -e line 1.
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