One should never, ever write "my $foo = 1 if /(foo)/;". From perlsub:
in reply to Re^4: = rather than =~ ? (too brief?)
in thread = rather than =~ ?
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.