The somewhat sucky way is: 

my $string= ' ' x 2**19;
$string= '';

[download]

It'd be cool if the following worked but it doesn't: 

length( $string )= 2**19; # Doesn't work

[download]

Or you can get creative: 

open NUL, "<", File::Spec->devnull();
sysread( NUL, $string, 2**19-length($string), length($string) );
close NUL;

[download]

Testing in my environment shows that you can even get away with: 

sysread( STDOUT, $string, 2**19 );

[download]

which leaves $string's current value unchanged while extending the storage allocated to it. Of course, there is a risk of running into a system where STDOUT is open for both read and write access. I wonder if there is another Perl built-in that reads into a buffer that can be used more conveniently.

Update: Testing also shows the following works well: 

sub grow
{
    sysread( DATA, $_[0], $_[1] );
}
__DATA__

[download]

- tye        

In reply to Re: Pre-grow a string (MTOW) by tye
in thread Pre-grow a string by diotalevi

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