Lots of ways. A few:

my $matches = 0;

while (...) {
    ++$matches;
    ...
}

if (! $matches) {
    ... "sorry no matches found"
}
[download]

or

my $command = $sth->fetchrow_arrayref();
if (! $command) {
    ... "sorry no matches found"
}
else {
    do {
        for (...) {
            printf ...
        }
    } while ($command = $sth->fetchrow_arrayref());
}
[download]

or

my $first = 1;
while ( (my $command = $sth->fetchrow_arrayref) || $first ) {
    if (! $command) {
        ... "sorry no matches found"
        $first = 0;
    }
    else {
        for ...
    }
}
[download]