Why is it printing multiple versions of the results?

Because you asked it to:

foreach my $key_expal (keys %expal) {
    $sth->execute($key_expal) || die $sth->errstr;
. . .
[download]

This means that for every entry in the %expal hash, the statement will be executed with that argument.

Since you don't have any placeholders in your statement, execute ought to fail in this case, since the params passed are used to fill-in placeholders.