I was poking around in Perl 5.8.0's core module library, and turned up a new form of open that I hadn't heard about. It happens in lib/5.8.0/{arch}/PerlIO/scalar.pm

Something I've occasionally wanted to do is to attach a file handle to a string as an accessor. That has been possible with earlier perl using IO::Scalar or IO::Stringy, but not all filehandle semantics and conventions were honored. I found that that is native in 5.8.0 with PerlIO, and that the syntax is as simple as could be imagined: open FILEHANDLE, MODE, SCALARREF.

That's it - give open a reference to the string in the file name slot, and it works. The handle may be read, written, or appended. Globals like $/ work as expected.

Here's a sledgehammer-on-peanut example which prints a string in cable-ese (upper case, suppressed spaces, five letter groups):

my $foo= 'Now is the time for all good men to come to the aid of their
+ country';
{
    local $\ = " ";
    local $/ = \5;
    $foo =~ tr/ //d;
    open my $fh, '<', \$foo;
    print uc while <$fh>;
}
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As an output file:

my $foo;
$_ = "She sells sea shells by the sea shore";
{
    local $\ = $/;
    open my $fh, '>', \$foo;
    print $fh $_ for split;
}
print $foo;
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Append, capturing STDERR:

my $oops;
open STDERR, '>>', \$oops;
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I've only started to explore this trick. I haven't tried flock or seek/tell or $.. I haven't tinkered with truncate or exotic modes.

Here's a challenge. Can you find any limits to file-like behavior? What cool uses can you think of for this?

After Compline,
Zaxo