You can use this simple JavaScript:
##example Results
##Macro Library @RegEx Change to Title Case
####DOWNLOAD:
<a class="attachment" href="/uploads/default/original/2X/6/6136d028821cebd23fca50a3fd92564637038c9c.kmmacros">@RegEx Change to Title Case.kmmacros</a> (2.0 KB)
---
<img src="/uploads/default/original/2X/a/aef4ffeb186e00faf28455d09151b10442d00147.png" width="458" height="616">
###JXA Script
```javascript
var kmeApp = Application("Keyboard Maestro Engine");
var sourceStr = kmeApp.getvariable('Source_String');
sourceStr.replace(/(^|[^a-z0-9])([a-z])/g,
function(m,m1,m2,p){ return m1+m2.toUpperCase(); }
);
```