Perl 6 in a hands-on test

Game Mode

Keyboard input from the command line usually requires the user to confirm each entry with the return key, but in game mode, you want the blackjack script to respond directly to key presses. The raw terminal mode is used for this on Unix systems; you will only want to enable this during the actual entry and reset to normal cooked mode immediately after; otherwise, the terminal no longer responds to shell commands typed after the program has exited.

This is why the prompt-char() function defined in line 56 (Perl 6 allows dashes in function names) uses the stty utility to run a shell command that enables raw mode and disables it again on leaving the routine. Perl 6 provides the keywords ENTER and LEAVE to perform actions when entering and exiting a function. From the $TTY file handle in the previously opened terminal, read(1) consumes a byte via the prompt-char() function, and the downstream decode() method converts the buffer byte to an ASCII character that the script can later compare with a letter such as "h" (hit) or "s" (stand).

Perl 6 has a switch statement, which goes by the name of given/when and is used in line 31 to compare the player's keyboard input with specified letters and initiate the corresponding game controls.

Perl 6 vs. Perl 5

The game flow in Listing 4 is pretty self-explanatory, and if you compare the lines of code required for the implementation, Perl 6 comes off slightly ahead. Also the dropped parentheses in the for and while loop heads have a positive effect on readability.

Will Perl 6 assert itself? It is probably too early to tell; production tests will decide the outcome. Larry Wall hinted that he was working on a Perl 6 book at the conference in Orlando but left open how long it will take to publish it. If you want to draw lessons from the past, then you might guess that a good chunk of time may pass between announcement and release in Larry's private empire.

Mike Schilli

Mike Schilli works as a software engineer in the San Francisco Bay Area. He can be contacted at Mike's homepage can be found at


  1. Schrodinger's cat:
  2. "Quantum Casino" by Michael Schilli, Linux Magazine, January, 2004, pg. 61:
  3. Listings for this article:
  4. Blackjack soft 17 rule:

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