You'll have to lc as appropriate but this covers path normalization pretty well.

use Path::Class;

my @file =qw(
           C:\dir\file.pl
           C:/dir/file.pl
           C:\dir\File.PL
);

for my $file ( @file )
{
    my $path = Path::Class::File->new($file);
    print $path->as_foreign("Win32")->absolute, $/;
}
#
C:\dir\file.pl
C:\dir\file.pl
C:\dir\File.PL
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