if (0) { print "This block is happening!\n"; use Win32; } print "$_\n" for keys %INC; __DATA__ Exporter.pm Carp.pm strict.pm vars.pm Config.pm warnings/register.pm warnings.pm DynaLoader.pm AutoLoader.pm Win32.pm <------- Perl sees all uses (almost) #### [root@devel3 root]# cat test.pl #!/usr/bin/perl -wT BEGIN{print "We are on $^O\n"} if ($^O eq 'MSWin32') { use Win32::TieRegistry( Delimiter=>"/", ArrayValues=>0 ); # load $config from registry } else { # else load $config from flat files } [root@devel3 root]# ./test.pl We are on linux Can't locate Win32/TieRegistry.pm in @INC (@INC contains: /usr/local/lib/perl5/5.6.2/i686-linux /usr/local/lib/perl5/5.6.2 /usr/local/lib/perl5/site_perl/5.6.2/i686-linux /usr/local/lib/perl5/site_perl/5.6.2 /usr/local/lib/perl5/site_perl) at ./test.pl line 4. BEGIN failed--compilation aborted at ./test.pl line 4. [root@devel3 root]#