perl启动后台进程

今天遇到一个perl启动后台进程的问题，就是是在启动命令后面加"&"的进程还是顺序，特做此小实验

a.pl调度

#!/usr/bin/perl -w

use Data::Dumper;

my $cmd1="perl b.pl &";
my $cmd2="perl b.pl &";

my @result=`$cmd1`;
my @result1=`$cmd2`;
#system($cmd1);
#system($cmd2);

print Dumper(@result),"\n";
print Dumper(@result1),"\n";

这种方式是确实是顺序执行的，但是用system调试是并行的。

b.pl

#!/usr/bin/perl -w

print $$." begin ".current(),"\n";
sleep 20;
print $$." end ".current(),"\n"; 


sub current
{
    my ($sec,$min,$hour,$mday,$mon,$year)  = localtime();
    $year += 1900;
    $mon ++;
    ($sec,$min,$hour,$mday,$mon,$year) = format_date($sec,$min,$hour,$mday,$mon,$year);
    return "$year-$mon-$mday $hour:$min:$sec";
}

sub format_date
{
    my(@items) = @_;

    my $pattern = "[-\/ :]+";

    foreach    my $item (@items)
    {
        $item = (length($item)==1) ? "0$item":$item;
    }

    return @items;
}