Some playing around shows it's not an exception:

#!/usr/bin/perl

my $string = "Bla\nBlo\nBloe";
print join("|", split('something', $string));
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This code is parsed as

~$ perl -MO=Deparse split.pl 
my $string = "Bla\nBlo\nBloe";
print join('|', split(/something/, $string, 0));
split.pl syntax OK
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The same goes for double quotes. split() expects a regex, but apparently will settle for things in quotes and interpret the string as a regex. Indeed, you live and learn :-)

Arjen