my 〜 if は未定義
元ソース何処だったかようやく見つけたのでメモ
perlsyn - Perl の文法 - perldoc.jp
注意: (my $x if ... のような) 条件構造やループ構造で修飾された my 文の振る舞いは 未定義 です。
NOTE: The behaviour of a my statement modified with a statement modifier conditional or loop construct (e.g. my $x if ... ) is undefined. The value of the my variable may be undef, any previously assigned value, or possibly anything else. Don't rely on it. Future versions of perl might do something different from the version of perl you try it out on. Here be dragons.
