Re^3: Using an IO::File object stored in a Hash.

Simply stated, its because the diamond operator does dual service as both readline and glob. If the value or variable inside looks like a file handle at compile time, then it is interpreted and compiled as readline, if it doesn't, then it is interpreted and compiled as glob. At compile time a hash element is deemed more likely to contain a glob pattern than a filehandle.

As for why, you'd have to ask the author(s), but it is probably a throwback to when perl didn't have lexical filehandles; and it's never been seen as high enough priority to attempt a fix.

With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

"Science is about questioning the status quo. Questioning authority". The enemy of (IT) success is complexity.

In the absence of evidence, opinion is indistinguishable from prejudice.

Comment on Re^3: Using an IO::File object stored in a Hash.

Replies are listed 'Best First'.
Re^4: Using an IO::File object stored in a Hash. by jjs04 (Novice) on Jan 20, 2017 at 19:14 UTC
Thank you very much! This is the explanation I needed. I found this in perlop in the I/O Operators section: "If what's within the angle brackets is neither a filehandle nor a simple scalar variable containing a filehandle name, typeglob, or typeglob reference, it is interpreted as a filename pattern to be globbed, and either a list of filenames or the next filename in the list is returned, depending on context. This distinction is determined on syntactic grounds alone. That means <$x> is always a readline() from an indirect handle, but <$hash{key}> is always a glob(). That's because $x is a simple scalar variable, but $hash{key} is not--it's a hash element. Even <$x > (note the extra space) is treated as glob("$x ") , not readline($x)."	[reply]

Replies are listed 'Best First'.

Re^4: Using an IO::File object stored in a Hash.
by jjs04 (Novice) on Jan 20, 2017 at 19:14 UTC

I found this in perlop in the I/O Operators section:

"If what's within the angle brackets is neither a filehandle nor a simple scalar variable containing a filehandle name, typeglob, or typeglob reference, it is interpreted as a filename pattern to be globbed, and either a list of filenames or the next filename in the list is returned, depending on context. This distinction is determined on syntactic grounds alone. That means <$x> is always a readline() from an indirect handle, but <$hash{key}> is always a glob(). That's because $x is a simple scalar variable, but $hash{key} is not--it's a hash element. Even <$x > (note the extra space) is treated as glob("$x ") , not readline($x)."

[reply]