if ($result_array) {
    print "something\n";
}
else {
    print "nothing\n";
}
[download]

Also, the DBI POD mentions checking $sth->err

Thanks toolic, exactly what I needed. I had the DOH moment just as I opened your response.
Paradise: Florida, full tank of gas, no appointments.

In one case you stringified it. In the other you are taking it in scalar context and Perl magic is not doing what you expect.

use strict; use warnings; use 5.010;

my @array = qw (there is some data here);
is_empty (\@array);

# look out for edge cases
@array = qw(one);
is_empty(\@array); 

#empty it
@array = ();
is_empty (\@array);

sub is_empty {
    my $array_ref = shift; 
    say "\nGot: ". join ", ", @{$array_ref};
    say "Empty" unless scalar @{$array_ref};
    say "Caution"           if $#{$array_ref}     ==  0;
    say "Empty"             if $#{$array_ref}     ==  -1;
    say "Maths == String?"  if @{$array_ref}      ==  "";
    say "Empty as String?"  if @{$array_ref}      eq  "";
}
[download]

Cheers,
R.

fetchall_arrayref returns zero if the query failed

my $result_array  = $sth->fetchall_arrayref;

if (!$result_array) {
   print "query failed!!\n";
}
[download]

If no rows are found (the query is successful, but no rows are returned) fetchall_arrayref returns a reference to an empty array.

my $result_array = $sth->fetchall_arrayref;

if ($result_array) {
    print "success\n";
    if (@$result_array) {
        print "found rows @$result_array\n";
    }
    else {
        print "no rows returned\n";
    }
}
else {
    print "query failed!!\n";
}
[download]