#!/usr/bin/perl
use strict;
use warnings;

my $a="  456 789 123 456 789  ";
my $count;
$count=$a =~ /\d+/g;
print "$count\n";    # output '1', position changes
$count=$a =~ /\d+/g;
print "$count\n";    # output '1' position changes

$count = () = $a =~ /\d+/g;
print "$count\n";  # output '3'

my @a = $a =~ /\d+/g;
$count = @a;
print "$count\n";