Argh... I thought I could do better, but to get your exact results, all I could come up with was:

my @fields = $string =~ m/([^|]*)\|?/g;
$string && $string !~ /\|$/ && pop @fields;
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That second line can get a bit simpler if you define an empty string to have zero fields instead of having a single null field.

Congrats, your solution is better than mine even though it looks unnecessarily complicated.

I think the best suggestion so far is to tell split how many fields you want:

my @fields = split(/\|/,$string,$string =~ tr/|/|/ + 1);
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Though I'd probably break it up into two lines:

my $fieldcount = $string =~ tr/|/|/ + 1;
my @fields     = split(/\|/, $string, $fieldcount);
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-Blake