use Symbol;

$sym = gensym;
open($sym, "filename");
$_ = <$sym>;

ungensym $sym;      # no effect

print qualify("x");              # "main::x"
print qualify("x", "FOO");       # "FOO::x"
print qualify("BAR::x");         # "BAR::x"
print qualify("BAR::x", "FOO");  # "BAR::x"
print qualify("STDOUT", "FOO");  # "main::STDOUT" (global)
print qualify(\*x);              # \*x--for example: GLOB(0x99530)
print qualify(\*x, "FOO");       # \*x--for example: GLOB(0x99530)