use strict; 

opendir(DIR, "./") or die $!;  # open current directory
my @files;
while (my $file = readdir(DIR)) {
    # Use a regular expression to ignore files beginning with a period
    push(@files, lc($file));
}
closedir(DIR);

# read the prompt.
my $promptfile = shift;
print STDERR "reading $promptfile\n";

open(PROMPT, $promptfile);
my $i = 0;
while (my $prompt = <PROMPT>) { 
    $i++;
    print STDERR $prompt . "\n";
    $prompt =~ s/^\d+\.\s//; # remove "93. ";
    $prompt = lc($prompt);
    
    # concat a list of .wav files corresponding to the prompt
    my $files = "";
    foreach my $word (split(/\s+/, $prompt)) {
        # choose a random file from the files, that beings with the gi
+ven $word.
        my @grepped = grep(/^$word/, @files);
        my $file = $grepped[ int(rand(scalar @grepped)) ]; # choose a 
+random file
        $files .= $file . " ";
    }
    my $output = sprintf("S%05d",$i);
    my $command = "sox $files $output.wav";
    print STDERR $command . "\n"; # TODO: add system call.
    system($command);
    print STDOUT "$output.wav $output.mfc\n";
}
close(PROMPT);
[download]

AFTER RUN THIS I GOT

Use of uninitialized value $file in concatenation (.) or string at scr
+ipts/conca
tprompt.pl line 29, <PROMPT> line 100.
sox           S00100.wav
sox FAIL sox: Not enough input filenames specified
[download]

AND COMMAND IS LIKE:

perl -w scripts/concatprompt.pl trainprompts > codetrain.scp
[download]

PLEASE TELL ME HOW TO REMOVE THIS ERROR...