Although not in one regex, this works:

use strict;

my $string = '|xx-xxx-xxxxx-xxx x/xx|xx-xxxx-xxx-xx-xxxx-xx-xx|';
print "$string\n";

$string =~ s/\|//;      # gets rid of the first pipe
$string =~ s/\|/,/g;    # replaces all other pipes by commas
print "$string\n";

my @chunks = split '-', $string;
$string = join( '-', @chunks[ 0 .. 3 ] ) . ','
    . join( ',', @chunks[ 4 .. $#chunks ] );
print "$string\n";
[download]

giving:

|xx-xxx-xxxxx-xxx x/xx|xx-xxxx-xxx-xx-xxxx-xx-xx|
xx-xxx-xxxxx-xxx x/xx,xx-xxxx-xxx-xx-xxxx-xx-xx,
xx-xxx-xxxxx-xxx x/xx,xx,xxxx,xxx,xx,xxxx,xx,xx,
[download]

Please note that it appears you also replace a space by a comma in your example.