Not specifically. The regex match is context sensitive, so the brackets around it enforce list context and then the [0] pulls out the first value of that list before the <=> gets a chance to enforce scalar context on it. Example:

#!/usr/bin/env perl 
use strict;
use warnings;
use feature 'say';

my $x = 'a-9';

say "Scalar: " . $x =~ /(\d+)/;
say "List:   " . ($x =~ /(\d+)/);
say "First:  " . ($x =~ /(\d+)/)[0];
[download]

Read lots more in the Context tutorial.