How do I conditionally add a space in a regex replace - regex

Question

When I woke up this morning, I didn’t know a stroke of regex. By the time I went to Mass, I’d been able to cobble together this regex to find occurrences of ‘Mph’ in an html document.
(?i)(?<=[\s|\d])mph+
If I run it against the following test data:
<div class="vsMph">
<p>95 Mph</p>
</div>
<div class="vsMph">
<p>95Mph</p>
</div>
It correctly matches:
‘ Mph’ and
‘Mph’
And equally correctly leaves the ‘vsMph’ alone, which is exactly what I want. Eventually, I'm going to use the same technique to match knots, ft, in, km and so on.
I’m executing this expression in in Sublime Text 3 using RegReplace and ultimately, what I hope to do is to use this regular expression to find all occurrences of ‘Mph’ preceded by a space or a digit and:
Enclose ‘Mph’ in <abbr> tags.
Add a space between the digit and the
opening <abbr> tag if there was no space between the last digit and
'Mph' originally.
In other words, I want to convert the above test data to:
<div class="vsMph">
<p>95 <abbr title="Miles per hour">Mph</abbr></p>
</div>
<div class="vsMph">
<p>95 <abbr title="Miles per hour">Mph</abbr></p>
</div>
I can get RegReplace to add the <abbr> tags as described in 1. above, but I’ve searched around on Google and I can’t find anything that tells me how to conditionally insert a space in a regex replace.
So I’m wondering. Is it possible in the first place to conditionally add a space in a regex replacement and if so how do I do it, or do I have to search for ‘\sMph’ and ‘\dMph’ and replace them separately?
Regards.

Answer 1

I would suggest using groups to match Mph. You could search for simply the following regex:
(\d)(\s)?(Mph)
Then replace using groups
$1 <abbr title="Miles per hour">$3</abbr>
output:
<div class="vsMph">
<p>95 <abbr title="Miles per hour">Mph</abbr></p>
</div>
<div class="vsMph">
<p>95 <abbr title="Miles per hour">Mph</abbr></p>
</div>