Well, I parsed variably structured strings, consisting of different characters, like: letters, numbers, space, brackets, minus, comma from a CSV file.

The CSV file is a database output in the form of an Excel worksheet, saved as a CSV file. The first coloumn contains fields with a series of letters and numbers, called IDs, i.e.

|A B 1234 a <1>|
|A B 1234 a,b|
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In order to look up the image files corresponding to the IDs, I parse the IDs of the CSV file into a text file, which will later be opened as a file handle. During the parsing of the IDs the comma of comma separated letters (like: a,b or c,e) which are part of the ID is accidentally (?) deleted.

Just to point out the context: The parsing is the first step of a file import, see nodes:

Read text file - Encoding problem?