use strict; use warnings ;

  use constant HOMBURG => 'HA' ;

  my %bar = (homburg => 'homburg!', HOMBURG => 'HomBurg!', HOMBURG, 'Ha!') ;
  print join(', ', %bar), "\n" ;

  my $k = HOMBURG ;
  print "\$k = HOMBURG  -> \$k=$k\n" ;
  print "\$bar{homburg}=$bar{ homburg }, \$bar{HOMBURG}=$bar{HOMBURG}, ",
               "\$bar{\$k}=$bar{$k}, \$bar{+HOMBURG}=$bar{+HOMBURG}\n" ;

##</code><code>##

  my $w = '0001' ; my $x = 'zlqq' ; my $y = '-zlxq' ; my $z = '+zlxq' ;

  print " \$w=$w,  \$x=$x,   \$y=$y,  \$z=$z\n" ;
  print "+\$w=", +$w, ", +\$x=", +$x, ",  +\$y=", +$y, ", +\$z=", +$z,"\n" ;
  print "-\$w=", -$w, ",   -\$x=", -$x, ", -\$y=", -$y, ", -\$z=", -$z, "\n" ;

##</code><code>##

  use strict; use warnings ;

  use constant HOMBURG => 'HA' ;

  print "-HOMBURG=", -HOMBURG, ", -foo=", -foo, "\n" ;

##</code><code>##

  my $x = '0x1234' ; my $y = 0x1234 ;

  printf "\$x=%s, ~\$x=%s\n", show($x), show(~$x) ;
  printf "\$y=0x%X, ~\$y=0x%X\n", $y, ~$y ;
  printf "hex(\$x)=0x%X, ~\hex($x)=0x%X\n", hex($x), ~hex($x) ;
  printf "\$y=%s,\n ~\$y=%s\n", show($y), show(~$y) ;

  sub show {
    return '"'. join('', map { sprintf('\\x%02X', ord($_)) } split(//, $_[0])) .'"' ;
  } ;

##</code><code>##

  use strict; use warnings ;

  my $z = <DATA> ;
  printf "\$z=%s, ~\$z=%s\n", show($z), show(~$z) ; 

  sub show {
    return '"'. join('', map { sprintf('\\x%02X', ord($_)) } split(//, $_[0])) .'"' ;
  } ;  

  __DATA__
  0x1234

##</code><code>##

  use strict; use warnings ;

  foreach my $z ('0', '0000', '+0', '-0', ' 0', '0 ', '0E0') { try($z) ; } ;

  sub try {
    my ($z)  = @_ ;
    my $bool = $z      ? 'True' : 'False' ;
    my $zero = $z == 0 ? '=='   : '!=' ;
    printf "%7s is %5s and %2s 0\n", "'$z'", $bool, $zero ;
  } ;