I think you might be able to put a method call inside a double-quoted string by surrounding it with list constructor and de-references like this

$result->execute()
   or print "Error while executing query --- @{[$result->errstr()]}";
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but whether you would want to is another matter as it looks a bit messy. If you have a call in the middle of a string then it might make more sense as you don't have to keep closing and opening quotes.

Cheers,

JohnGG