How did Perl gain a reputation (deserved, undeserved, or used to be deserved, no longer so) of being a "write only language"?

Was it

• The syntax of the language
• Specific features that were available in the language
• Specific features not being available in the language (or at least old versions of it)
• The kind of tasks Perl was being used for
• The kind of people who use Perl (people who aren't full-time programmers)
• Criticism from people committed to another language
• Something else?

Background: I'd like to know if some aspects that gave Perl the reputation of being write-only also apply to other languages (specifically ruby).

Disclaimer: I recognise that Perl doesn't force people to do write-only code (can any language?), and that you can write bad code in any language.