While I agree that awk and Perl 4 have roughly comparable powers, I would not call Perl "a superset of awk" (At least not Perl 3/4; I'm not familiar with the syntax of earlier versions).
Where awk really shines is situations that call for a set of record based production rules, and if in fact your problem is in that domain, you could write hundreds or even thousands of rules without the problem becoming unsuitable for awk. Like for any domain specific language, you could consider the limitations imposed by awk as valuable discipline to keep you in the problem domain.
While perl can be written in an awk-like style, it's really much more of a general purpose language, so it can accommodate workflows that deviate substantially from the "sequentially process records" style that awk excels at.
The autosplit and loop options to Perl make it very suitable for an awk replacemnt. It even has BEGIN and END pseudo-patterns.
Once you've tried Perl you don't want to flip back and forth to awk because the inconsistencies in syntax (within and to each other) will drive you mad.
Where awk really shines is situations that call for a set of record based production rules, and if in fact your problem is in that domain, you could write hundreds or even thousands of rules without the problem becoming unsuitable for awk. Like for any domain specific language, you could consider the limitations imposed by awk as valuable discipline to keep you in the problem domain.
While perl can be written in an awk-like style, it's really much more of a general purpose language, so it can accommodate workflows that deviate substantially from the "sequentially process records" style that awk excels at.