Perl - custom keystroke handlers - perl

Question

I'm trying to implement custom handlers for given keystrokes so that I can change mode when my script is fetching data from file. How is that possible without any WHILE loop?
I was looking into Term::ReadKey but I dont think it does what I need. Maybe I should connect it with something though I can't find any solution on google.
I've just started with perl scripting :)

Answer 1

Here is an example of how to avoid busy waiting when waiting for a keyboard input:
use strict;
use warnings;
use IPC::Open2;
my $pid1 = run_cmd('read_key');
my $pid2 = run_cmd('counter');
print "Master: waiting for keyboard event..\n";
waitpid $pid1, 0;
print "Master: Done.\n";
kill 'TERM', $pid2;
sub run_cmd {
my ($cmd) = #_;
open(OUT, ">&STDOUT") or die "Could not duplicate STDOUT: $!\n";
open(IN, ">&STDIN") or die "Could not duplicate STDIN: $!\n";
my $pid = open2('>&OUT', '<&IN', $cmd);
return $pid;
}
where read_key is:
use strict;
use warnings;
use Term::ReadKey;
ReadMode 4;
END { ReadMode 0 }
my $key = ReadKey(0);
print "$key\n";
and counter is:
use strict;
use warnings;
$SIG{TERM} = sub { die "Child (counter): Caught a sigterm. Abort.\n" };
my $i = 0;
while (++$i) {
sleep 1;
print "$i\n";
}
Example output:
Name "main::IN" used only once: possible typo at ./p.pl line 19.
Name "main::OUT" used only once: possible typo at ./p.pl line 18.
Master: waiting for keyboard event..
1
2
3
q
Master: Done.
Child (counter): Caught a sigterm. Abort.