HyperZonk and Synapse0 have both suggested that the my is being ignored and all that is happenning is that $x is simply global.

It's a good theory, and certainly what I thought when I first looked at it. But it's easy to see that this isn't true: try comparing

sub foo{
  my $x if 0;
  print "FOO: ", $x++, "\n";
}
sub bar{
  my $x if 0;
  print "BAR: ", $x--, "\n";
}
foo, bar for (1..10);
[download]

with

sub foo{
  print "FOO: ", $x++, "\n";
}
sub bar{
  print "BAR: ", $x--, "\n";
}
foo, bar for (1..10);
[download]

I reckon the real reason is the explanation given by Abigail.

Now I don't think I would ever write my $x if 0 unless I wanted to get the sack for writing obscure code, but how about:

sub STATIC_VARIABLE{ 0 }

sub foo{
  STATIC_VARIABLE && my $x;
  print "FOO: ", $x++, "\n";
}
[download]

would that be difficult to understand? Would it carry on working in the future?

-- iakobski