Can you show me the output of the following code? It's a slightly modified version of your original code. According to you the else-branch should trigger if there's nothing to be read from /dev/dsp1.

#!/usr/bin/perl

use strict;
use warnings;

# input device
my $input = "/dev/dsp1";

# open filehandler
open(my $fh, '<', $input) or die("ERROR open $input ($!)\n");
binmode($fh);

while(1) {
    my $buffer;

    # read one byte
    read($fh, $buffer, 1);

    if(defined($buffer)) {
        # ignore
    }
    else {
        print "nothing to collect\n";
    }
}

close($fh);
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If the else-branch does indeed trigger then I wonder what's going on. From my understanding of Perl the if-condition is always true, even if there's nothing to be read.

#!/usr/bin/perl

use strict;
use warnings;

open my $fh, '<', '/dev/null';
binmode($fh);

my $buffer;

# read one byte
read($fh, $buffer, 1);

if(defined $buffer) {
    print "read something\n";
}
else {
    print "nothing to collect\n";
}
[download]

read something

#!/usr/bin/perl

use strict;
use warnings;

open my $fh, '<', '/dev/null';
binmode($fh);

my $buffer;

# read one byte
my $r = read($fh, $buffer, 1);

if($r > 0) {
    print "read something\n";
}
else {
    print "nothing to collect\n";
}

close($fh);
[download]

nothing to collect