Reminds me of working with free-form, manual entry order detail information, in a former life.
Hundreds of thousands of records a month. I ended up importing them into Excel(1) and then using... what was that called? An MS/Windows library that came with IE 5 and/or a few other things, that provided regex support (with a few quirks) that was accessible via VBA.
The point was, I could programmatically mine it -- including regex pattern matching and replacement of and within cell contents -- while also having a flexible UI within which to find and handle one-off cases. When the one-off's demonstrated a repeating pattern, I could quickly iterate to add that to the programmatic mining logic.
This included adding color cueing for items of particular interest, manual follow-up. Excel's sorting capabilities to bring potentially related instances into visually displayed groups. And the like.
It ended up working quite well. I might have preferred something else to VBA, and I did use Perl and other stuff, elsewhere (something that also gave me both power and the flexibility to rapidly iterate).
But the point is, with such data, I found it very useful to combine regex and rapid programmatic manipulation, together with a good visual interface (including visual cues, the ability to comment upon instances -- Excel cell-level comments -- etc.) and manual manipulation.
As a final aside, the extensive set of Excel keyboard shortcuts greatly aided in rapidly and effectively navigating and massaging the imported data.
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1. This was back when Excel had... I think it was a 64K (or a bit less) limit on the number of rows in a sheet.
P.S. I tended to retain the originally imported data in its columns, and to produce my mining of it in other columns. That way, I could always and immediately see what I started with, for any particular record. (And, if things visually started to be "too many columns", well, Excel lets you hide a range of columns from the view. As one example of how its features really helped, on the visual front while doing this work.)
I still had to learn and allow for some quirks Excel exhibited with respect to importing text data. That included making sure the cells/columns being imported into carried the correct/needed formatting designation before importing into them (usually, "Text").