I remember vaguely that AmigaOS kept some remnants of this convention. Not from Pascal but from sth called B/CPL. A few (small majority) of system functions took arguments in this peculiar [<len><string>] format.

Afaik AmigaOS itself was based on some earlier OS written in B or BCPL language.

PS: Here's some story behind this http://aminet.net/package/dev/misc/BCPL