Difference in Perl regex variable $ {name} and $-{name}-CodePudding

What is the difference between Perl regex variables $ {name} and $-{name} when both are used to refer to the same regex group from Perl statement/expression code?

CodePudding user response：

While $ {name} holds the captured substring referred by name as a scalar value, $-{name} refers to an array which holds capture groups with the name.
Here is a tiny example:

#!/usr/bin/perl

use strict;
use warnings;

'12' =~ /(?<foo>\d)(?<foo>\d)/; # '1' and '2' will be captured individually

print $ {'foo'}, "\n";          # prints '1'

for (@{$-{'foo'}}) {            # $-{'foo'} is a reference to an array
    print $_, "\n";             # prints '1' and '2'
}

As $ {name} can hold only a single scalar value, it is assigned to the first (leftmost) element of the capture groups.