"Use at least more than one operating system"
Redhat and Debian? ;-)
Of course, Perl is more geared towards programmers wanting all the world to be like (some incarnation of) Unix, but across with unixish operating systems ranging from HPUX over Linux to OSX, many assumptions don't hold true.
Yeah, but don't overdo it. The other extreme (which you find voiced on Perlmonks every now and then) is the assumption that every piece of Perl code should run on every platform under the sun (where "every" often turns out to be "Linux" and "Windows"). I wouldn't be surprised if more than 90% if the code written out there is written to solve a particular problem/requirement/job for a particular machine. It doesn't make sense to spend an effort in making your small script cross-platform if it's going to cost millions to port the environment it runs in to a different platform. It'll be a wasted effort.

In reply to Re^3: What should you know before you start to learn Perl? by JavaFan
in thread What should you know before you start to learn Perl? by luis.roca

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