use v5.12;
use warnings;

STDOUT->autoflush;
my $doit;
my $input;

while ( my $line = <STDIN> ) {
    unless ( defined $doit ){
        $doit = $line;
        last if $doit eq "EOF";
        next;
    }

    if ($line eq "$doit") {
        doit();
        undef $doit;
    } else {
        $input .= $line;
    }
}

say "exit by $doit";
exit;

sub doit {
    print "((( STDOUT ::: $doit";
    print $input;
    print "))) STDOUT ::: $doit";
    #warn "STDERR:",$input," ";
    $input ="";
}