Perl is awesome. Perl’s docs are awesome. The Perl community is … awesome. However, the language is fairly large and arguably complex. For those Perlers who long for a simpler time, a more orthogonal language, and elegant OO features built-in from the beginning, Ruby may be for you.

Similarities

As with Perl, in Ruby,...

• You’ve got a package management system, somewhat like CPAN (though it’s called RubyGems)
• Regexes are built right in. Bon appétit!
• There’s a fairly large number of commonly-used built-ins.
• Parentheses are often optional
• Strings work basically the same.
• There’s a general delimited string and regex quoting syntax similar to Perl’s (looks like %q{this (single-quoted)}, or %Q{this (double-quotish)}, and %w{this for a single-quoted list of words}. You %Q|can| %Q(use) %Q^other^ delimiters if you like).
• You’ve got double-quotish variable interpolation, though it "looks #{like} this" (and you can put any Ruby code you like inside that #{}).
• Shell command expansion uses `backticks`.
• You’ve got embedded doc tools (Ruby’s is called rdoc).

Differences

Unlike Perl, in Ruby,...

• You don’t have the context-dependent rules like with Perl.
• A variable isn’t the same as the object to which it refers. Instead, it’s always just a reference to an object.
• Although $ and @ are used as the first character in variable names sometimes, rather than indicating type, they indicate scope ($ for globals, @ for object instance, and @@ for class attributes).
• Array literals go in brackets instead of parentheses.
• Composing lists of other lists does not flatten them into one big list. Instead you get an array of arrays.
• It’s def instead of sub.
• There’s no semicolons needed at the end of each line. Incidentally, you end things like function definitions, class definitions, and case statements with the end keyword.
• Objects are strongly typed. You’ll be manually calling foo.to_i, foo.to_s, etc., if you need to convert between types.
• There’s no eq, ne, lt, gt, ge, nor le.
• There’s no diamond operator. You usually use IO.some_func instead.
• The fat comma is only used for hash literals.
• There’s no undef. In Ruby you have nil. nil is an object (like anything else in Ruby). It’s not the same as an undefined variable. It evaluates to false if you treat it like a boolean.
• When tested for truth, only false and nil evaluate to a false value. Everything else is true (including 0, 0.0, and "0").
• There’s no PerlMonks. Though the ruby-talk mailing list is a very helpful place. And we’ve also got a wiki and a faq.