#! perl -slw
use strict;
use Inline C => 'DATA', NAME => 'fmode', CLEAN_AFTER_BUILD => 0;

open FILE, $ARGV[0] or die "'$ARGV[0]:$!";

printf "%x\n", fmode( \*FILE );


__DATA__
C:\test>fmode "<junk.dat"
1

C:\test>fmode ">junk.dat"
2

C:\test>fmode ">>junk.dat"
2

C:\test>fmode "+<junk.dat"
80

C:\test>fmode "+>junk.dat"
80

C:\test>fmode "+>>junk.dat"
80

__C__
int fmode( FILE *stream ) {
    return stream->_flag;
}