You are not defining an anonymous sub, you are trying to call a subroutine with the name generated from the block:

&{ 
   # code here returns a value,
   # that's interpreted as the name
   # of the subroutine to call...
 }
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You need something like:

my $subroutine = sub {
     # code here defines an anonymous sub
};

$subroutine->( @arguments ); #call sub
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You should ask yourself what you want to do with your example: do you want to define a subroutine, call it or both?

In your case, I would just use an unless statement:

unless ($newSeriesSth->execute()) {
   # error handling
}
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Anonymous subs (esp. closures) are of much more use when you need callbacks.

-- 
Joost       downtime n. The period during which a system
            is error-free and immune from user input.
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