BEGIN simplifies multi-platform programs

[blssu]

If you have a program that must run on several platforms, use BEGIN to load platform specific versions of your utility routines. This eliminates tests in your main code and cleanly isolates non-portable code.

## file myapp
use strict;

BEGIN {
    if ($^O eq 'MSWin32') {
        require MyAppWin32
    }
    else {
        require MyAppUnix
    }
}

print "HOME is '", get_home_dir(), "'\n";

## file MyAppWin32.pm
package main;

use Win32::TieRegistry ( Delimiter => '/' );

sub get_home_dir {
    my $key = $Registry->{'HKEY_CURRENT_USER/Software/Microsoft/Window
+s/' .
                          'CurrentVersion/Explorer/Shell Folders'};
    scalar($key->GetValue('Personal'))
}

1;

## file MyAppUnix.pm
package main;

sub get_home_dir {
    (getpwuid($<))[7]
}

1;

[rob_au]

This can be easily performed with the if module - For example:

use if ( $^O eq 'MSWin32' ), 'MyAppWin32';
use if ( $^O ne 'MSWin32' ), 'MyAppUnix';

 

perl -le 'print+unpack("N",pack("B32","00000000000000000000001000011100"))'