And when I find "serious.txt", Is there a way I can immediatly stop all the other threads from completing?

By that I assume you to mean that you want searching to cease once you have found something that matches all your targets.

NOTE: As coded, the things to search for are themselves used as regex. As such, you need to escape any meta characters on the command line. It is also case sensitive. I consider these a bonus for the application shown, but you may wan't to change one or the other.

#! perl -slw
use strict;
use threads qw[ async ];
use threads::shared;

our $DRIVES ||= 'C';

die "Nothing to search for" unless $ARGV[ 0 ];

sub runAndCheck {
    my( $cmd, $foundRef, $doneRef, $lookfor ) = @_;
    my $pid = open CMD, "$cmd |" or die "$cmd : $!";
    while ( my $line = <CMD> ) {
        chomp $line;
        last if keys %$lookfor == grep defined, values %$lookfor;
        $line =~ $_ and $lookfor->{ $_ } = $line for keys %{ $lookfor 
+};
    }
    close CMD;
    kill 1, $pid;
    $$doneRef = 1;
}

my @cmds = map{ "attrib /s $_:\\* " } split '', $DRIVES;
my @found  : shared;
my @dones  : shared = ( 0 ) x @cmds;
my %lookfor: shared; @lookfor{ @ARGV } = ();

async{ 
    runAndCheck( 
        $cmds[ $_ ],
        \@found,
        \$dones[ $_ ],
        \%lookfor        
    );
}->detach for 0 .. $#cmds;

sleep 1 while grep( $_, @dones ) < @cmds;

if( grep defined, %lookfor ) {
    printf "%20s : %s\n",
        $_, defined $lookfor{ $_ } 
        ? " was found at '$lookfor{ $_ }'"
        : " was not found."
            for keys %lookfor;
}
else {
    print "None of @ARGV were found";
}
[download]

Some examples runs:

P:\test>412014 -DRIVES=CDPR junk\.htm$ 412014 copyrght  \bcmd\.exe  CM
+D\.EXE
          junk\.htm$ :  was found at 'A          C:\Perl\test\junk.htm
+'
          \bcmd\.exe :  was not found.
            copyrght :  was found at '     R     R:\copyrght.htm'
              412014 :  was found at 'A          C:\Perl\test\412014.p
+l'
            CMD\.EXE :  was found at 'A          C:\WINDOWS\SYSTEM32\C
+MD.EXE'

P:\test>412014 -DRIVES=PDR junk\.htm$ 412014 copyrght  \bcmd\.exe  CMD
+\.EXE
          junk\.htm$ :  was found at 'A          P:\test\junk.htm'
          \bcmd\.exe :  was not found.
            copyrght :  was found at '     R     R:\copyrght.htm'
              412014 :  was found at 'A          P:\test\412014.pl'
            CMD\.EXE :  was not found.

P:\test>412014 -DRIVES=PDR junk\.htm$ 412014 copyrght  cmd\.exe  CMD\.
+EXE
            cmd\.exe :  was not found.
          junk\.htm$ :  was found at 'A          P:\test\junk.htm'
            copyrght :  was found at '     R     R:\copyrght.htm'
              412014 :  was found at 'A          P:\test\412014.pl'
            CMD\.EXE :  was not found.

P:\test>412014 junk\.htm$ 412014 copyrght  cmd\.exe  CMD\.EXE
            cmd\.exe :  was found at 'A          C:\Program Files\Clas
+sic PhoneTools\inssuitecmd.exe'
          junk\.htm$ :  was found at 'A          C:\Perl\test\junk.htm
+'
            copyrght :  was not found.
              412014 :  was found at 'A          C:\Perl\test\412014.p
+l'
            CMD\.EXE :  was found at 'A          C:\WINDOWS\SYSTEM32\C
+MD.EXE'
[download]