my @tests = ( '', qw(
    2|3|||||
    2
    2|
    2|3
    2|3|
    |
    |2
    |2|
    |2|3
    |2|3|
));


for my $string (@tests) {

    # Splits on '|' and preserves empty fields...
    my @fields = $string =~ m/((?:^|(?<=\|))[^|]*)/g;

    printf "%-10s :", "'$string'";
    print "($_)" for @fields;
    print "\n";
}
__END__
''         :()
'2|3|||||' :(2)(3)()()()()()
'2'        :(2)
'2|'       :(2)()
'2|3'      :(2)(3)
'2|3|'     :(2)(3)()
'|'        :()()
'|2'       :()(2)
'|2|'      :()(2)()
'|2|3'     :()(2)(3)
'|2|3|'    :()(2)(3)()

##</code><code>##

    my @fields = split /\|/, $string.'|x'; pop @fields;