$ perl -Mwarnings -Mstrict -E '
    my $str = "  a   |  b|c   |d|0|   ";
    my @fields = map { $_ ||= ""; s/^\s*(.*?)\s*$/$1/; $_; } split /[|]/ => $str;
    say ">>>$_<<<" for @fields;
'
>>>a<<<
>>>b<<<
>>>c<<<
>>>d<<<
>>><<<
>>><<<