https://en.wikipedia.org/w/index.php?title=Honsh%C5%AB%E2%80%93Shikoku_Bridge_Project&oldid=672031445

If there are two date fields with 2 different values: Just pick any date field. I am OK with that.

I searched 65% of the July 2015 database dump for regex "Expert-subject.*Expert-subject". 50 matches i.e. much less to fix.

@GoingBatty would you like to have a go?

@Magioladitis - Will do. Some of the articles found have {{expert-subject}} in different sections, so they aren't appropriate to be combined.

@Magioladitis - I found 50 articles in the Sep 2015 dump and fixed about 25 of them using the following Regex:

• FIND: {{expert-subject\s*\|(.*?)\|date\s*=\s*\w+ \d{4}}}\n?{{expert-subject\s*\|(?:1\=)?(.*?\|date\s*=\s*\w+ \d{4})}}
• REPLACE: {{expert-subject|$1|ex2=$2}}

I then had to tweak (or revert) the results when templates had "section" and/or "reason", or when there were three templates. For others, when one template was at the top of the article, I could remove a redundant template that was in a section.
Thanks!

So, in fact we only have to fix the following example case

FIND:
{{Expert-subject|Foo|date=Some date}}
{{Expert-subject|Bar|date=Some different or same date}}

REPLACE:
{{Expert-subject|Foo|ex2=Bar|date=Some date}}

And do nothing if any of the two templates has 3 or more parameters.

You could also choose to merge templates if the reason and/or talk parameters are the same:

FIND:
{{Expert-subject|Foo|reason=fubar|date=Some date}}
{{Expert-subject|Bar|reason=fubar|date=Some different or same date}}

REPLACE:
{{Expert-subject|Foo|ex2=Bar|reason=fubar|date=Some date}}

FIND:
{{Expert-subject|Foo|talk=Fubar|date=Some date}}
{{Expert-subject|Bar|talk=Fubar|date=Some different or same date}}

REPLACE:
{{Expert-subject|Foo|ex2=Bar|talk=Fubar|date=Some date}}

Too much complexion for a few pages...