Above you told it to split on pipes. And what I get when I run it is "Hello\" which is split on pipes.

Are you trying to split on pipes except when preceded by a backslash? If so:

#!/usr/bin/perl
use strict;

my $id = 'Hi|Hello\|Sir';
my @code = split(/[^\\]\|/,$id);

print $code[1]."\n";
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Note: That since this now splits on a character followed by a pipe that $code[0] would be "H" and not "Hi". The short answer is you are looking for split to have a variable delimiter in this case. A pipe sometimes and no pipe at other times.