My first suggestion is to always, always check the status of your DBI calls, like so:

my $sth=$dbh->prepare($MYSQL) or die "Could not prepare $MYSQL: $DBI::
+errstr\n";
...etc. for all connects, executes, etc.
[download]

As far as passing spaces, that should not be a problem. When you execute the query, the DBI should quote it for you. Try adding the line

$dbh->trace(2);
[download]

at the top of your script (after $dbh is created, of course) to see some of the details of what is going on. You could also use the 'quote' function to see exactly what it is sending:

my $string = "find me";
my $newstring = $dbh->quote($string) or die "Could not quote $string: 
+$DBI::errstr\n";
print "($string) has become ($newstring)\n";
[download]

('quote' is mostly used to help escape characters like a single apotrophe, which has special meaning inside SQL.)

Finally, consider moving your SQL statements into a variable: it will read better, be easier to maintain, and eliminate double typing of the same string in multiple places:

my $bazfind = shift || "12";

print "Looking for $bazfind.\n";

my $dbh=DBI->connect($SID, $user, $pass, {AutoCommit=>1}) 
  or die "Could not connect to $SID: $DBI::errstr\n";

my $FOOBAR_SQL = "SELECT FOO FROM BARVILLE WHERE BAZ=?";

my $sth=$dbh->prepare($FOOBAR_SQL) 
  or die "Could not prepare $FOOBAR_SQL: $DBI::errstr\n";

$sth->execute($bazfind)
  or die qq!Could not execute $FOOBAR_SQL with "$bazfind": $DBI::errst
+r\n!;

...etc. etc.
[download]

Note how the single declaration of $FOOBAR_SQL not only saves typing it in repeated times, but looks nicer too.