read(0,

##</code><code>##

#!/usr/bin/perl -w
use strict;
$SIG{CHLD} = 'IGNORE';

my $pid = fork(); die $! unless defined $pid;
unless ($pid) {
    # run background program to watch
    exec q(exec perl -E 'for (1..10) {say "...working"; sleep 1} <>');
    exit;
}

sub check {
    my $pid = shift;
    my $pid2 = open my $strace, "-|", "strace -qp $pid 2>&1" or die $!;

    local $SIG{ALRM} = sub { kill INT => $pid2 };
    print "checking...\n";
    alarm 3;
    my $trace;
    $trace.=$_ while <$strace>;
    alarm 0;
    close $strace;

    if ($trace =~ /^read\(.*$/) {   # check strace output
        print "=> hanging\n";
        kill TERM => $pid;    # (optional)
        return 0;
    } else {
        print "=> still running\n";
        return 1;
    }
}

0 while check($pid);

__END__
$ ./964971.pl
checking...
...working
...working
...working
=> still running
checking...
...working
...working
...working
=> still running
checking...
...working
...working
...working
=> still running
checking...
...working
=> still running
checking...
=> hanging