[burke]

Awk and perl.

I use a lot of bash though.

[ChrisArgyle]

About 7 years ago I had a job where we supported almost every Unix all the way back to AT&T SVR3 (including OpenServer, UnixWare, HP-UX, AIX, Linux, OSF/1). With the exception of SVR3 every single one had binary packages for Perl 5.

[ausjke]

until you run embedded routers and such, where perl is too large and bash/ash/mush rules.

[peterwwillis]

Or you're bootstrapping an install process and perl isn't included, but a shell is.