Mutagens

• Make regular expressions work backwards:

  use overload;
  
  BEGIN {
      overload::constant qr => sub {
          return reverse shift();
      };
  }
  
  print "It worked!\n" if "foo" =~ /oof^/;

  
  
• Make subroutine calling case-insensitive:

  sub AUTOLOAD {
      no strict 'refs';
      goto &{lc $AUTOLOAD};
  }
  
  sub foo {
      print "It worked!\n";
  }
  
  FoO();

  
  
• Initialise all global variables to zero:

  CHECK {
      while (my($n,$v) = each %::) {
          $$v = 0 if !defined $$v;
      }
  }
  
  print "It worked!\n" if defined($any_variable)
                       && $any_variable == 0;

  
  
• Everything should be printed backwards:

  sub TIEHANDLE {my $x; bless \$x}
  sub PRINT {
      shift;
      print REALOUT map scalar reverse, reverse @_;
  }
  open(REALOUT, ">&STDOUT");
  tie *STDOUT, "main";
  print "\n!dekrow", " tI"

Extensions

• I'm an lvalue subroutine. Was I called in lvalue or rvalue context?

  use Inline C => <<NOMO;
  
  U8 wantlvalue ()
  {
      return cxstack[cxstack_ix].blk_sub.lval;
  }
  
  NOMO
  
  sub foo :lvalue {
      print (wantlvalue() ? "lvaluably\n" : "rvaluably\n");
      my $foo
  }
  
  foo();
  foo() = 23;

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