I don't have UFT 12.0x anymore but I do have both 11.53 and 12.51
In UFT 11.53 and UFT 12.21 there are a few different "Replace" items in the help menu.
There are two that stand out to me:
This is what I typically use, and it has up to 6 parameters.
All are listed in the help.
"Replace Method (VBScript)"
This only has two parameters and is explicitly a RegExp method.
It is confusing seeing it labelled as "VBScript", but it is correctly described in the help as being a RegExp method.