Strict is there to protect you from silly programming errors, and to enforce good practice. Writing perl without strict is like operating a Chainsaw with the safety guards removed. It might be a bit faster but sooner or later you will come to regret it.

My advice is to get used to programming with strict, and to avoid the use of global variables. (Which are a problem with mod_perl in any case). How hard is it to wrap your main code in a function and declare variables as local to that function?

Just write:

#!perl

sub main
{
  my $variable = 42;
  my $result = library_call($variable);
  # more code
}

# other subroutines.

exit main();
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It's very annoying to pass to each function the 'global' variable , is there an alternative to do this ?

You could also have a look at web-frameworks like Catalyst or Dancer which have probably solved all the problems or annoyances you are now struggling with.

the another thing I can't understand is:

First you need to realize that mod-perl and perl are approximately in sync. I just updated and tested a perl cgi script on a server without mod-perl enabled, and then had to debug it again under an enabled mod-perl server. Several functions of perl just don't work the same under mod-perl and error messages may or may not exist. But for performance, mod-perl if great.

To handle the global problem, just keep your 'my's in scope:

   #!/usr/local/bin/perl -w
   {
      use strict;
   
      my $global = 3; my %Hash = ();
      my $result = Get_Result();
      print "Result: $result\n";
      exit;      ## Optional, but I prefer to show exits.
   
      sub Get_Result
      {   return( $global * 10 );
      }
   
   }
   
   1;
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Result: 30
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For passing variables to subroutines, I use a hash/array in the main scope, and pass the reference to it to out-of-scope subroutines.

my $Hash_result = Out_of_Scope( \%Hash);
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If you use one master hash, then all subroutines can be written the same way. Saves on typing if you just copy a skeleton subroutine, rename it and then add the code you need.

Good Luck