This is easy using threads::async

#! perl -slw
use strict;
use threads qw[ async ];
use threads::shared;

$|=1;
my $done:shared = 0;
my $rc  :shared = 0;
async {
    system @ARGV;
    $rc = $? >> 8;
    $done = 1;
};
my $n=0;
printf "%s\b", substr '|/-\ ', ($n = ++$n % 4), 1
    while select( '','','',0.25) and not $done;

print "@ARGV : rc = $rc";

__END__
P:\test>499224 perl -e"sleep 10; exit 123"
perl -esleep 10; exit 123 : rc = 123
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