$ perl -Mstrict -MPOSIX -wE 'my $pid = fork; if( $pid ){ kill TERM => $pid; foreach( 1..5 ){ sleep 1; waitpid $pid => WNOHANG; my $rv = kill 0 => $pid; say $rv; exit unless $rv; } kill KILL => $pid; waitpid $pid => 0;  } else { BEGIN{ $SIG{TERM}=sub{ say "TERM!"; }; } sleep 3;  exit; }'
TERM!
1
1
0
$ perl -Mstrict -MPOSIX -wE 'my $pid = fork; if( $pid ){ kill TERM => $pid; foreach( 1..3 ){ sleep 1; waitpid $pid => WNOHANG; my $rv = kill 0 => $pid; say $rv; exit unless $rv; } kill KILL => $pid; waitpid $pid => 0;  } else { BEGIN{ $SIG{TERM}=sub{ say "TERM!"; }; } sleep 5;  exit; }'
TERM!
1
1
1
$