Simple script for batching tasks in a multi-core/CPU envionment

Today I was tasked with keeping all four processors of a machine busy with CPU intensive processes (in this case transcoding video). I wrote a quick and dirty Perl script to keep running ffmpeg as input files became available, but never run more that four at a time. The script looks for .avi files in the directory from which it was executed. It then maintains a stack of file names, forks a child process for each file and moves it when done.

#!/usr/bin/perl

use POSIX ":sys_wait_h";
use Errno qw(EAGAIN);

$secs = 5;

$numProcs = 0;
$maxProcs = 4;

$fileExt = ".avi";

@files = ();
%was_processed = {};

while (1) {
    #print "numProcs = $numProcs\n";
    if($numProcs < $maxProcs) {
	$numProcs++;
	execNext();
    }
    my $reaped = reapNext();
    if($reaped > 0) {
	$numProcs--;
    } elsif ($numProcs == $maxProcs) {
	#print "Sleeping...\n";
	sleep $secs;
    }
}

sub reapNext {
    return waitpid(-1, &WNOHANG);
}

sub execNext() {
    my $file;
    WAIT_FOR_NEW_FILE: {
	getFiles();

	while($was_processed{$file = pop @files}) {}

	if(!defined $file) {
	    print "Waiting for new $fileExt files...\n";
	    sleep $secs;
	    redo WAIT_FOR_NEW_FILE;
	} else {
	  $was_processed{$file} = 1;
	}
    }
    doFork($file);
}

sub getFiles {
    if($#files == -1) {
	push @files, <*$fileExt>;
    }
}

sub doFork {
    my $file = @_[0];
  FORK: {
      if($pid = fork) {
	  #We are in the orig process
	  return;
      } elsif (defined $pid) {
	  #We are in a child process
	  doChild($file);
      } elsif ($! == EAGAIN) {
	  #Something is wonky, but we should be able to recover...
	  sleep 5;
	  redo FORK;
      } else {
	  die "Can't fork: $!\n";
      }
    }

}

sub doChild {
    my $file = @_[0];
    (my $name, my $junk) = split /$fileExt/, $file;
    print "Ripping $file\n";

    system "(ffmpeg -i \"$file\" -acodec libfaac -ab 128k -ac 2 -vcodec libx264 -b 1500k -bf 2 -f mpegts -aspect 4:3 -y \"$name\.ts\" 2>&1) > \"$name\.log\"\n";
    system "(mv \"$file\" ripped  2>&1) >> \"$name\.log\"\n";

    #unlink "\"$name\.ts\.mpeg\"";#delete the ts file
    #sleep $secs + rand $secs;

    exit;
}