Thanks

That helps my understanding of the problem and suggests to me that I am not going to be able to parse my data using a single regex

I could change the data, perhaps using ',,' for a non-splitting comma instead of '\,' which I can't differentiate from '\\,'

No.

Look again at your output

1
This is a problem->\,B
2
[download]

this output is correct, it is *not* a problem...

For the last part of your comment

instead of '\,' which I can't differentiate from '\\,'
[download]

If you would restate that as double-quoted strings it would look like this

instead of "\\," which I can't differentiate from "\\,"
[download]

which is true, but not what you meant, you meant to say (in double-quoted strings)

instead of "\\," which I can't differentiate from "\\\\,"
[download]

which you can and have done.

In a single-quoted string, the backslash ONLY does quoting if it occurs before a ' or a \
otherwise it stands for itself. That's why '\,' and '\\,' actually represent the same string.

Try looking at the printed string instead of the perl form of the string to see what you actually have.

I understand that in a single quoted string '//' is the same as '/' and looking at the printed string

my $text = '1,This\, is a problem->\\,B,99';
print "$text\n";
> output
1,This\, is a problem->\,B,99
[download]

I can see this.

Whilst, as you point out, I can get a regex to work correctly, I still can't get the output that I need. '//' is the same as '/' so I am never going to be able to 'differentiate' the two, or have I still not grasped it!