PERL expression

   Synopsis:
      Executes a mini-Perl programme

   Notes:
      This is the equivalent of a Perl command typed in the 'main' window's
         command entry box.
      The expression is run as a mini-Perl programme. The programme's return
         value (if any) is executed as an instruction. If the Perl programme
         generates an error, no instruction is executed.
      The instruction is typically a world command that's sent straight to the
         world, but it can be any kind of Axmud instruction except another Perl
         command.
      If the Perl command produces any kind of error, the Axbasic script
         continues as normal. No Axbasic error message is generated.

      Extensive help for Perl commands is available by typing ';help perl'.
      See also the help for MULTI, SPEED and BYPASS.

   Examples:
      ! Run a quick Perl programme
      PERL " $a = 'hello'; $b = 'world'; $a . $b; "
