Run a subroutine in the background until a condition - perl

Question

How could I rewrite this so that info runs in the background until a $aw is equal result?
#!/usr/bin/env perl
use 5.12.0;
use warnings;
use Term::ReadLine;
my $term = Term::ReadLine->new( 'something' );
$term->ornaments( 0 );
sub info {
# in the real script this runs some computations instead of the sleep
# and returns some information.
my ( $time ) = #_;
sleep $time;
return $time * 2;
}
my $value_returned_by_info = info( 10 ); # run this in the background
my $aw;
$aw = $term->readline( 'User input: ' );
if ( $aw eq 'result' ) {
# if info() is still running in the background:
# wait until info() returns because "$value_returned_by_info" is needed.
say $value_returned_by_info;
}
else {
# if info() is still running in the background:
# let info() in the background because "$value_returned_by_info" is not needed here.
say $aw;
}
$aw = $term->readline( 'User input: ' );
if ( $aw eq 'result' ) {
# if info() is still running in the background:
# wait until info() returns because "$value_returned_by_info" is needed.
say $value_returned_by_info;
}
else {
# if info() is still running in the background:
# let info() in the background because "$value_returned_by_info" is not needed here.
say $aw;
}
$aw = $term->readline( 'User input: ' );
if ( $aw eq 'result' ) {
# if info() is still running in the background:
# wait until info() returns because "$value_returned_by_info" is needed.
say $value_returned_by_info;
}
else {
# if info() is still running in the background:
# let info() in the background because "$value_returned_by_info" is not needed here.
say $aw;
}
say "End";

Answer 1

I agree with user5402. The mention of running in the background and the sleeping info function raise a lot of questions.
I wonder if maybe you're looking for a more tidy way of re-prompting for input when the given input is not correct. If that's the case, then maybe the IO::Prompter module works for you.
#!/usr/bin/env perl
use 5.10.0;
use strict;
use warnings;
use IO::Prompter;
sub info {
my ($time) = #_;
sleep $time;
return $time * 2;
}
my $expect = info(10);
my $aw;
PROMPT:
{
$aw = IO::Prompter::prompt( 'Enter number', -i );
if ( $aw eq $expect ) {
say "$aw :)";
}
else {
say "$aw :(";
redo PROMPT;
}
}
say "End";

Answer 2

If info can run in a separate process then you can just use fork. Otherwise you will have to use a threaded version of perl.
Example of using fork:
sub start_info {
my #params = #_;
my $pipe;
my $pid = open($pipe, "-|");
if (!$pid) {
# this code will run in a sub-process
# compute $result from #params
# and print result to STDOUT
sleep(10);
my $result = "p = $params[0] - pid $$";
print $result;
exit(0);
};
my $r;
return sub {
return $r if defined($r);
$r = <$pipe>; # read a single line
waitpid $pid, 0;
$r;
};
}
sub prompt {
print "Hit return: ";
<STDIN>;
}
my $info1 = start_info(4);
prompt();
print "result = ", $info1->(), "\n";
my $info2 = start_info(30);
prompt();
print "result = ", $info2->(), "\n";