I have been working on a command line script that makes several system calls, some of which take a few seconds (minutes?) to return. The long pauses give the impression that the script has hung, which isn't great. I figured I could address this by adding some kind of visual "still processing" feedback, like an hourglass or pinwheel. Because it's just a command line script, I do it with dots.
My code is below. I would appreciate any feedback or suggestions for improvement. Thank you.

use strict;
use threads;
use threads::shared;

sub SystemCall {
    my $call = join ' ', @_;
    local $| = 1; # run hot pipes
    print "Executing system call '$call'";

    # Start a thread to print out dots indicating that Perl hasn't hun
+g
    my $thread_beat = 0.1; # Should be small, but not so small as to f
+lood the screen with dots.
    my $stop :shared = 0;
    my $thread = threads->create( {'context' => 'void'}, sub {
        while ( not $stop ) { print '.'; select( undef,undef,undef, $t
+hread_beat ) }
    });
    $thread->detach();

    # Run the command
    my $result; 
    eval { chomp( $result = `$call` ) };
    warn $@ if $@; # eval failed.

    # Signal the thread to end.
    $stop = 1;
    # And wait one beat for the thread to end.
    select( undef,undef,undef, $thread_beat + 0.01 );
    print $/;

    # Present error message status, if any.
    warn "\$? = '$?'\n" if defined $? and $?;
    warn "\$! = '$!'\n" if defined $! and $!;
    warn "\$@ = '$@'\n" if defined $@ and $@;
    warn "\$^E = '$^E'\n" if defined $^E and $^E;
    warn "\$^W = '$^W'\n" if defined $^W and $^W;

    if ( $result ) { print $result, $/ }
    return defined $result ? $result : '';
}

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In reply to Using a thread to provide visual feedback. by Anonymous Monk

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