If you have an array reference that you "know" will only contain one item, then it sounds like you just want to access the first element of the array:

my $result = db_execute($SQL)->[0];
my ($title, $body) = @{$result};

# or

my ($title, $body) = @{db_execute($SQL)->[0]};
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Check out perlref, perllol and especially perldsc for information about references and the ways you can use them.