Dear Monks, The simplest script #!/usr/bin/perl use strict; use warnings; print "Hello, World...\n"; Works fine in my computer (Printing in the CMD screen "Hello World") but in other computers did not print anything on the screen after installing the same perl version. What is happening?

That's pretty unusual, and I think you'll have to explain exactly how you're calling this script on both computers so we can help you better. Since you say "CMD" I guess this is Windows? Are you using ActivePerl or Strawberry Perl, and what version? When you open the command prompt on both computers and type perl -v, it should output the same thing; that's assuming your PATH environment variable is set up correctly; if for example you're using the portable edition of Strawberry Perl, you'll have to navigate to its folder first (Update: or use its batch file to start the shell). It should also do the same when you type perl scriptname.pl for your script filename. Or, are you double-clicking the scripts to run them? Note that this sometimes requires additional steps to get working. (By the way, please use <code> tags to format code and data.)

G'day ferbio,

Welcome to the Monastery.

The most likely cause is your shebang line: '#!/usr/bin/perl'. On one computer, perl is installed in /usr/bin/; on another computer, it's installed elsewhere.

You need to tell us which OSes you're using and show all output. It seems odd that you get no output at all: perhaps no "Hello, World...", but were there any other messages. Here's what I get when I try to run perl from both an existing and non-existing location:

$ /usr/bin/perl -e 'print "Hello, world!\n"'
Hello, world!

$ /usr/not_bin/perl -e 'print "Hello, world!\n"'
-bash: /usr/not_bin/perl: No such file or directory
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Putting your posted code — but using an invalid path to perl in the shebang line — into a script and running:

$ cat crap.pl
#!/usr/not_bin/perl

use strict;
use warnings;

print "Hello, World...\n";

$ ./crap.pl
-bash: ./crap.pl: /usr/not_bin/perl: bad interpreter: No such file or 
+directory
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Take a look at perlintro for a gentle introduction of this concept; perlrun has a more detailed discussion.

If the second computer is not running windows, we also need to know anything you can tell us about its operating system and perl. Are you using the perl that was shipped with the OS?

#!/usr/bin/perl
use strict;
use warnings;
print "Hello, World...\n";
[download]

If that's not it I have no idea what you're doing because any other interpretation of your post would throw an error from something. Putting it in a file will at least give you a feedback if that's not where your perl is located.

Further reading

«The Crux of the Biscuit is the Apostrophe»

perl -MCrypt::CBC -E 'say Crypt::CBC->new(-key=>'kgb',-cipher=>"Blowfish")->decrypt_hex($ENV{KARL});'Help

I don't know why you would do that? That appears unnecessary to me. I guess that is like a null option. On Windows, the Perl path in the shebang line is ignored but options after that path like perhaps -w are parsed and used. I don't think a double dash followed by nothing means anything on any OS.

-- is how you'd generally denote options for something else other than the first executable that's being called.

For example for perl, perlrun says that: A -- signals the end of options and disables further option processing. Any arguments after the -- are treated as filenames and arguments..

What this means roughly, IIRC, is that you use it to pass of options after -- to the perl script you're calling with perl.

For example,

$ perl -MSome::Module ./myperlscript.pl -- --my-opt1 foo --my-opt2 bar
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What this also means, I think, is that it's useless when part of the shebang line. Or maybe not, idk. Seems odd being in the shebang, though.

Update - after thinking about it, I can see how this might be considered a defensive programming tactic. E.g., if somehow some script kiddie was seeking the add options to your shebang, having -- would make anything after moot. Similarly, adding __END__ at the end of your perl scripts would also neutralize someone blindly appending to your files.

Lol. Its bait. (OT) Fixing Line Endings