Firstly, a very simple signal handling script: 
#!/usr/bin/perl

use common::sense;
use Glib qw/TRUE FALSE/;

$SIG{USR1} = \&on_usr1;

my $loop = Glib::MainLoop->new( 'default', FALSE );
$loop->run;

sub on_usr1 {
    my $sig = shift;
    say "somebody told me $sig";
}

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If I call him, it will say: 
$ ./t_signal.pl &
[1] 2637
$ kill -s USR1 2637
somebody told me USR1
$ kill -s USR1 2637
somebody told me USR1
$

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However, if I create and open a named pipe for read, like this: 
#!/usr/bin/perl

use common::sense;
use Glib qw/TRUE FALSE/;

my $file_pipe = "pipes/$$".'_pipe';
system('mkfifo',$file_pipe)==0 or die $!;
my $p_read;
open $p_read,'<',$file_pipe or die $!;

$SIG{USR1} = \&on_usr1;

my $loop = Glib::MainLoop->new( 'default', FALSE );
$loop->run;

sub on_usr1 {
    my $sig = shift;
    say "somebody told me $sig";
}

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and send USR1 using kill, it just crashes: 
$ ./t_signal_1.pl &
[1] 2638
$ kill -s USR1 2638
$ 
[1]+  User defined signal 1   ./t_signal_1.pl
$

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Why?

In reply to problems on signal handling, Glib mainloop, and named pipe by llancet

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