The behaviour of 

my $x = 0 if 1 == 2;

[download]

is documented as undefined.

The problem is that you get the compile-time effect of my (declaring the variable) without the run-time effect (clearing the variable).

Lexicals variables are permanently allocated. They are cleared on scope exit, not freed.

The recursive effects are related to existence of a copy of the lexicals for every layer of recursion. 

sub f {
  my ($n) = @_;
  my $x if 0;
  print ++$x, "\n";
  f($n-1) if $n>1;
}

f(3); # 1,1,1
f(2); # 2,2
f(3); # 3,3,2

[download]

Update: Added bit about recursion.

In reply to Re: Confusion over scope of "my" vars by ikegami
in thread Confusion over scope of "my" vars by Anonymous Monk

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