mantra2006,
It sounds like what you want is alarm. The code would look something like:

print $time_out_request_msg;
my $time_out = <STDIN>;
chomp $time_out;
if (valid_timeout($time_out)) {
    $SIG{ALRM} = sub { # ... };
    alarm $time_out;
}
while (1) {
    # ...
}
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Update: The original node was modified by mantra2006 a couple of times after this reply so this reply may no longer be pertinent as a result.