Perl is not tied to any one vendor
Perl isn't tied to the health of a company or the whims of stockholders. Perl will still be supported even if the stock market crashes or Silicon Valley slides into the ocean.
Perl lets you do things your way
Don't be trapped by a vendor's proprietary development tools! Perl can talk to most major databases and is able to administer most operating systems so that you can build tools that solve your needs, rather than what the vendor thinks you need.
Many vendors have Perl development tools
Many products, such as Cybercash's e-commerce product, Cash Register, ship with Perl development tools. If you already have Perl skills in your enterprise, you'll be able to leverage those products more quickly than your competitors.
Perl is cross-platform
Although Perl started out on Unix, it runs on the Macintosh and on Microsoft platforms, along with many other operating systems. Developers can easily produce cross-platform programs by following the guidelines in the Perl documentation. Even Microsoft supports the development of Perl by working with ActiveState Tool Corp. to keep Perl running on Win32 and NT. If Microsoft likes Perl, shouldn't you?
Perl is open source software
Perl isn't a black-box. Anyone can look at the source, and many have. This means bugs get spotted and fixed sooner, and intermediate releases and patches are available very quickly. You don't have to wait for a big company's telephone support to tell you to upgrade when the new version is available.
Perl is mature
Perl has been around since 1987 - several years before the Web even. There has been plenty of time to shake the bugs out to deliver a stable product. It's now in version 5. Are your other tools as mature as Perl?
Perl is a high level language
High level languages speed up the development process. If you need a prototype for a big project, you can get it done very quickly in Perl (although many have reported that the prototype was so good it became the production version). Programmers spend less time thinking about things like memory management and variable typing and more time on what the product does best.
Perl handles memory management internally
Perl handles memory management so that programmers don't have to spend time creating memory management bugs which are the most frequent source of security holes.
Perl is secure
Perl has a special "taint" mode that closely scrutinizes user input to avoid common security problems. Using Perl's "taint" mode forces programmers to code more carefully.
Perl works with existing C libraries
Through either the XS or SWIG interfaces, Perl programs can use your legacy C libraries.