open my $fh, $somefile or die $!;

##</code><code>##

    sub on {
        my $file = shift;
        local \*F;
        open F, $file or die "Couldn't open $file: $!";
    }

##</code><code>##

C:\>perl -e "open my $fh, q|< test.txt| or die $!;print ref $fh"
GLOB