$ perl -MScalar::Util=reftype -le'open my $fh, "<", \$buf; print reftype($fh)'
GLOB

##</code><code>##

$ perl -le'open my $fh, "<", \$buf; print $fh; printf "0x%x\n", 0+$fh'
GLOB(0x814ec28)
0x814ec28