The problem:

I want to run code until the user hits a key (I don’t care which key). In old fashioned BASIC it’s simple:

count! = 0
DO
  datain$ = INKEY$
  count! = count! + 1
LOOP UNTIL LEN(datain$) > 0

PRINT count!
[download]

Running this for about a second results in half a million iterations. But I can’t work out how to do the same thing in Perl.

I have tried:

One way:

use strict;
use warnings;
use diagnostics;

my $count = 0;
my $char;

until (sysread STDIN, $char, 1) {
    $count++;
}
print $count;
[download]

Another way, based on Perl cookbook recipe 15.6:

use strict;
use warnings;
use diagnostics;
use Term::ReadKey;

my $count = 0;
my $char;

ReadMode('cbreak');

while ($char eq "") {
    $char = ReadKey(0);
    $count++;
}

print $count;
[download]

What happens:

Both respond in the same way. They sit until a key is pressed, and then return 1. I've only waited for up to five seconds, but even if I get multiple iterations by waiting longer, it's not nearly fast enough. I think what is happening is that the code is being optimised too far, but I would welcome clarification on this. I don’t actually need the counter in the finished code – I’m trying to initialise a series of pseudo-random number generators, but that code isn’t relevant to this particular part of the problem. The counter is just there to satisfy me that something is happening.

TIA and regards,

John Davies

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