This (waitpid returning) may be the case with OP's legacy environment.

Current perl appears to set up the signal handlers with SA_RESTART. In this case, the (wait4) syscall returns ERESTARTSYS and is automatically restarted by the libc wrapper. 

#! /usr/bin/perl

use strict;
use warnings;

$SIG{QUIT} = "IGNORE";

my $pid = fork() // die;
unless ($pid) {
    exit !exec "sleep 100";
}

$SIG{ALRM} = sub { warn "SIGALRM\n" };
$SIG{QUIT} = sub { warn "SIGQUIT\n" };

warn "childpid = $pid\n";
alarm(2);

warn "interrupted\n" while waitpid(-1, 0) == -1 and $!{EINTR};

[download]

Your advice is sound, however. Periodic polling is a hackish workaround. Unix has interrupts (^C ^\), and where possible, one ought to go with those. The alternative it to handle SIGCHLD and just keep reading/selecting on STDIN.

In reply to Re^2: Allowing user to abort waitpid by Anonymous Monk
in thread Allowing user to abort waitpid by lab007

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