Regular Expression (RegExp) syntax for Caller ID modification
If you need to modify Caller ID (add\remove plus, add\remove country code, etc.), you can use the Regular Expression (RegExp) on event handler settings window:
Add the valid regular expression and replacement string next to the %NUMBER% named placeholder in brackets: %NUMBER%(/regexp/replacement string/).
In the example below the ^1 is regular expression and +1 is the replacement string:
http://example.com?callerid=%NUMBER%(/^1/+1/)
You can perform multiple search and replace modifications on the input Caller ID string with the following syntax:
http://example.com?callerid=%NUMBER%(/(?=^..........$)/+1/;/^1/+1/)
In the example above /(?=^..........$)/+1/ adds +1 at the beginning if phone number contains 10 digits and /^1/+1/ replaces the first 1 with +1.