Personally, I eschew the use of trailing conditionals, and I can see that using them with 'my' is pathological. Best to use the ternary conditional operator '?:' with 'my'.

sub foo {
  my $string = ($conditional1) ? 'appended stuff' : '';
  $string .= 'more appended stuff' if ($conditional2);
}
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If you wanted your variable to remain undefined when the conditional is false, you can use:

  my $var = ($conditional) ? 'assigned value' : undef;
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