Use quotemeta. This will escape all non-alphanumeric characters. The problem you are running into is the "|" is being interpreted as an "or" in the regex, so you split at "nothing" or "nothing", so it splits the string at every character(equivalent to split(//, $str). Code Sample:

my $str = "1|2|3";
my $delimiter = #get delimiter
$delimiter = quotemeta($delimiter);

print "$_\n" foreach(split(/$delimiter/, $str));

__OUTPUT__
1
2
3
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