From the keyboard of Peter Scott [13.09.06,09:20]:
> Here's a distillation of something that just bit me, behaves the same on
> 5.6.1 and 5.8.5. Observe the following program:
Try this :-)
$_ = "bar";
print "before the loop: \$_ = $_\n";
for (1..1) {
print "before print_file(): \$_ = $_\n";
print_file($0);
print "after print_file(): \$_ = $_\n";
}
sub print_file {
print "before while: \$_ = $_\n";
local @ARGV = shift;
while (<>) { print }
print "after while: \$_ = $_\n";
$_ = "foo";
}
print "before __END__: \$_ = $_\n";
__END__
gives:
before the loop: $_ = bar
before print_file(): $_ = 1
before while: $_ = 1
$_ = "bar";
print "before the loop: \$_ = $_\n";
for (1..1) {
print "before print_file(): \$_ = $_\n";
print_file($0);
print "after print_file(): \$_ = $_\n";
}
sub print_file {
print "before while: \$_ = $_\n";
local @ARGV = shift;
while (<>) { print }
print "after while: \$_ = $_\n";
$_ = "foo";
}
print "before __END__: \$_ = $_\n";
__END__
after while: $_ =
after print_file(): $_ = foo
before __END__: $_ = bar
> Before running it, can you tell:
> Will it succeed or not?
> If not, with what error?
> Where?
> Why?
The error is thrown at the moment the <> oprator tries to assign to $_,
which is an alias to a constant - the '1'.
Common pitfall ;-)
The <> operator does no further aliasing, it operates upon $_ at it's
"current aliasing level".
0--gg-
--
_($_=" "x(1<<5)."?\n".q·/)Oo. G°\ /
/\_¯/(q /
---------------------------- \__(m.====·.(_("always off the crowd"))."·
");sub _{s,/,($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e,e && print}
