Twigils and special variables

I could not find a better place yet to introduce them so let me do it now. Perl 6 has a large set of special variables. In order to make it easy to differentiate them from regular variable they are marked with what we call a twigil. Regular, user defined variables have a sigil ($, @ or %) in front of them. System variables have and additional character between the sigil and the name of the variable.

Examples:

• $*PROGRAM_NAME

  contains the path to the currently running Perl 6 script.

• $*CWD

  contains a path to the current working directory.

• $*IN

  Is the standard input (STDIN). You can read a line using $*IN.get