It still stuck, not alarmed for some reasons. My code right now has become: 
sub process_scheme{
    my ($output_file) = @_;
    open (OUTPUT_FILE, ">", $output_file) || die "cannot open log file
+";
    my $scheme_pid = open (SCHEME, "./t.pl | ") || die "cannot pipe sc
+heme";
    my $str = "";
  MAIN:
    while (1) {
        eval{
            local $SIG{ALRM} = sub { die "alarm\n" }; # NB: \n require
+d
            alarm 5;#$allow_time;
            if (eof(SCHEME)){    
                close OUTPUT_FILE; close SCHEME;
                last MAIN;
            }
            $str = <SCHEME>;
            alarm 0;
        };
        if ($@) {
            close OUTPUT_FILE;
            kill $scheme_pid;
            close SCHEME;
            return -$current_player;
        }

        # process the line
        print OUTPUT_FILE $str;
    }
    return 1;
}

[download]
where the t.pl is 
while(1){};

[download]
The script gets stuck, waiting forever, not stopping/returning anything

In reply to Re^5: Cannot catch ALRM signal for timeout by Magice
in thread Cannot catch ALRM signal for timeout by Magice

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.