And yet another Perl-ish way to check the OS is to look at $^O (or if you use English, you can check it as $OSNAME). For instance something like the following would work:

use English;

BEGIN {
 if ( $OSNAME =~ /MSWin32/i) {
     #do some stuff for Windows
 } elsif ( $OSNAME =~ /solaris/i) {
     #do some stuff for solaris
 }#
}#end BEGIN
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You could put in whatever the various OSes are that you would need.