Perl将打印另存为变量

Question

I have a command

print $_->{href} . "\n" for $mech->find_link_dom(text_regex => qr/pdf/i);

that prints out the exact link I would like to save as a variable. Although when I try to do

my $link = $_->{href} . "\n" for $mech->find_link_dom(text_regex => qr/pdf/i);

it does not work.

Any thoughts?

Answer 1

If you know that $mech->find_link_dom(text_regex => qr/pdf/i) returns exactly one element, then you can write:

my $link = [$mech->find_link_dom(text_regex => qr/pdf/i)]->[0]->{href} . "\n";

If it can return multiple elements — or zero elements — then maybe you mean this:

my $link;
$link .= $_->{href} . "\n" for $mech->find_link_dom(text_regex => qr/pdf/i);

Answer 2

Your first code snippet is equivalent to:

for $_ ($mech->find_link_dom(text_regex => qr/pdf/i)) {
    print $_->{href} . "\n"
}

The second is equivalent to:

for $_ ($mech->find_link_dom(text_regex => qr/pdf/i)) {
    my $link = $_->{href} . "\n";
}

So, the $link variable is local to the for block, and is not visible outside of that block. It will work if you first declare the variable outside of the block:

my $link;

for $_ ($mech->find_link_dom(text_regex => qr/pdf/i)) {
    $link = $_->{href} . "\n";
}

Or, using the short form as in your code:

my $link;

$link = $_->{href} . "\n" for $mech->find_link_dom(text_regex => qr/pdf/i);