modruby.net

A Ruby block starts with `<%' and ends with `%>'. eRuby replaces the block with its output.

  $ cat foo
  Hello, <% print "World!" %>
  $ eruby foo
  Hello, World!

If `<%' is followed by `=', eRuby replaces the block with a value of the block.

  $ cat bar
  Hello, <%= "World!" %>
  $ eruby bar
  Hello, World!

If `<%' is followed by `#', the block is ignored as a comment.

  $ cat baz
  Hello,<%# this is
  a comment %> World!
  $ eruby baz
  Hello, World!

If a line starts with '%', eRuby evaluates the line as a Ruby program and replaces the line with its output.

  $ cat quux
  % x = 1 + 1
  1 + 1 = <%= x %>
  $ eruby quux
  1 + 1 = 2