Question

I found a possible bug in perl’s closures and $1 regexp variables. Simply, they don’t mix together.

Let’s take this code.

use warnings;

while ("1234567890"=~/(.)/sg) {
    push @subs, sub{print $1;};
}

for (@subs) {$_->()}

You would imagine that perl will now print all the numbers – instead, I got 10 warnings from undefined $1.

Is it really a bug, or did I just missed something in perl documentation? Is there some reason, why should $1 be undefined and NOT being part of the closure?

Answer 1

I think the answer is similar to the answer to perl closures and $_. $1 is a global variable, too.

What you need to do is:

my $x = $1;
push @subs, sub{print $x;};