From type/IO/Handle

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method opened(IO::Handle:D: --> Bool:D)

Returns True if the handle is open, False otherwise.

From type/IO/CatHandle

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method opened(IO::CatHandle:D: --> Bool:D)

Returns True if the invocant has any source handles, False otherwise.

say IO::CatHandle.new      .opened; # OUTPUT: «False␤» 
say IO::CatHandle.new($*IN).opened; # OUTPUT: «True␤» 
 
(my $f1 = 'foo'.IO).spurt: "A\nB\nC";
with IO::CatHandle.new: $f1 {
    .opened.say; # OUTPUT: «True␤» 
    .slurp;
    .opened.say; # OUTPUT: «False␤» 
}