use strict;
use Win32::Process::Info;
use Win32::Process;

Win32::Process::Info->Set(variant=>'WMI');
my $pi = Win32::Process::Info->new();
for($pi->ListPids){
    my ($info) = $pi->GetProcInfo($_);
    if($info->{CommandLine} eq 'perl foo.pl a'){
         my $obj;
         my $pid = $info->{ProcessId};
         Win32::Process::Open($obj,$pid,1);
         $obj->Kill(0);
         print "Killed $pid\n\n";
    }
}