Trimming an extended information field

[Dotcom1970]

I've noticed when pulling album catalogue numbers from discogs, and displaying them in a custom field, sometimes they have more than one.

e;g: TICK001CD, TICK001CD, TICK001CD, TICK001CD

How can I create a reg expression to grab that first catalogue number where commas separate multiples?

Currently, my custom field is as follows:

Name: CATALOGNUMBER
Value: $upper(%catalognumber%)
Field: %catalognumber%

[LyricsLover]

You want to reduce multiple appearances of the same content in CATALOGNUMBER to one entry?

Or do you want the first entry only, ignoring what other contents follow?

[Dotcom1970]

In that pictured example, they are all the same, but in others, they may be different - all I want is the first listed.

[LyricsLover]

You could adapt

RegExp to extract text before first comma

This is not quite true if you use $regexp(%composer%,'^(.+?),.*',$1) instead The potential section following the comma does not necessarily need the parenthesis if you do not want to use it anyway, so $2 is not mandatory. ... but there are so many ways to solve the problem.

and use

$regexp(%CATALOGNUMBER%,'^(.+?),.*',$1)

[LyricsLover]

BTW:
The term "trimming" as used in your title question is not exactly what you want to do.

"Trimming" in the scripting world means "to cut away leading or trailing whitespaces":

[Dotcom1970]

Apologies for using the wrong term. I'm very much a novice at this.