How to create a message external to Pegasus that has hyperlinks

For many years, I have been generating emails by having a PerfectScript macro create a text file, and then running F:\PMAIL\winpm-32.exe  -J ... .

 Now I need to move on (and up!): I need to put links to web pages in these emails.

How can I do it?

 Looking at my code, I see that the .txt file contains !M:70, !T:0, SY:1, TO: @LIST6F75.PML etc. lines, but I no longer have the info on what these parameters mean.