Chapter 17
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  #!/usr/bin/perl -w
  # Classic “Hello World” as done with Perl
  print “Hello World!\n”;
  
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  #!/usr/bin/perl -w
  # Create a file that will have a directory listing of user’s home dir
  print “About to read user’s home directory\n”;
  # open the home directory and read it
  opendir(HOMEDIR, “.”);
  @ls = readdir HOMEDIR;
  closedir(HOMEDIR);
  print “About to create file dirlist.txt with a directory listing of user’s
  home dir\n”;
  # open a file and write the directory listing to the file
  open(FILE, “>dirlist.txt”);
  foreach $item\; (@ls)\; \{\; print\; FILE$item .”\n”;
  }
  close(FILE);
  print “All done\n\n”;
  }
  
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  # Global variable $name\; is\; given\; a\; name$name = Paul
  # Enter our loop
  foreach (@filedata) {
  # declare a new variable for just the loop
  my $current\_file\_file;\; \#\; create\; a\; local\; version\; of\; name\; to\; temporarily\; assign\; values\; within\; the\; \#\; loop\; to\; local$name
  ...
  }
  
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  while ( counter . “\n”;
  $counter++;\; \}\; --------------------------------------\; do\; \{\; print$counter . “\n”;
  $counter++;\; \}\; while\; ($counter < 10);
  
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  foreach $temp\; (@authors)\; \{\; print$temp . “\n”;
  }
  
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  if ( $name\; eq\; ‘Paul’\; )\; \{\; print\; “Hi\; Paul\backslash n”;\; \}\; elsif\; ($name eq ‘Joe’) (
  print “Hi Joe\n”;
  } elsif ($name\; eq\; ‘Jeremy’)\; \{\; print\; “Hi\; Jeremy\backslash n”;\; \}\; else\; \{\; print\; “Sorry,\; have\; we\; meet\; before?\; “;\; \}\; --------------------------------------\; \#!/usr/bin/perl\; -T\; \#\; check.pl\; \#\; A\; Perl\; script\; that\; checks\; the\; input\; to\; determine\; if\; \#\; it\; contains\; numeric\; information\; \#\; First\; set\; up\; your\; Perl\; environment\; and\; import\; some\; useful\; Perl\; packages\; use\; warnings;\; use\; diagnostics;\; use\; strict;\; my$result;
  # Next check for any input and then call the proper subroutine
  # based on the test
  if (@ARGV) {
  # If the test condition for data from standard in is true run
  # the test subroutine on the input data
  ARGV[0].” has “.$result.”\; elements\backslash n\backslash n”;\; exit\; (0);\; sub\; test\; \{\; \#\; Get\; the\; first\; array\; element\; from\; the\; global\; array\; ARVG\; \#\; assign\; it\; to\; a\; local\; scalar\; and\; then\; test\; the\; local\; variable\; \#\; with\; a\; regular\; expression\; my$cmd_arg = $ARGV[0];\; if($cmd_arg =~ m/[0-9]/) {
  return (‘numeric’);
  } else {
  # There was a error in the input; generate an error message
  warn “Unknown input”;
  }
  }
  sub error {
  # There was no input; generate an error message and quit
  die “Usage: check.pl, (<INPUT TO CHECK>)”;
  }
  
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