Your code appears to work here (ubuntu linux, perl 5.8.8).
This is using backticks (not a system call, as you have in your code. All I did was to replace the extApp $_ with sleep 5.
Can you give some info on your platform and perl version please, and also let us know what the following script prints on your system?
#!/usr/bin/perl
use strict;
use warnings;
my @result;
$SIG{ALRM} = sub {
print "ALARM fired\n";
die "timeout";
};
eval {
alarm(3);
@result = `sleep 5`;
alarm(0);
};
print "Running after alarm: $@\n";
if ($@) {
if ($@ =~ /timeout/i) {
push @result, "App has hanged itself\n";
} else {
alarm(0); # clear the still-pending alarm
die; # propagate unexpected exception
}
}
print "result is: ", join('', @result), "\n";
I get:
ALARM fired
Running after alarm: timeout at tt.pl line 8.
result is: App has hanged itself
On a side note, when you propagate the 'die' error, it's best to re-throw the original die object/text with
die $@ to give higher-level code a chance of working out what went wrong.