Here is basically how you would run sox thru system.

#!/usr/bin/perl
use warnings;
#converts 8bit wav files to 16bit

my @files = <*.wav>;
  foreach my $file(@files){
     my ($name) = $file =~ /(.*).wav$/;
    system("sox -b $name.wav  -w $name.16.wav");
}
[download]

Do you mean an eSpeak Voice file? Perhaps you could provide more detail when asking a question, to remove any ambiguity. See How do I post a question effectively?.

Update: When updating a post, mark it as such, otherwise replies may look out of context.

Martin