Have you tried Carp? Seems to work — at least for a simple case like this:

#!/usr/bin/perl

use Carp;

eval {
    local $SIG{ALRM} = sub { croak "timed out" };
    alarm 3;

    # ...
    
    # have it hang in line 12
    my $s = <STDIN>;

    # ...
    
    alarm 0;
};

print "$@\n" if $@;
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Output (if you let it time out):

timed out at ./645816.pl line 6
        main::__ANON__('ALRM') called at ./645816.pl line 12
        eval {...} called at ./645816.pl line 12
        eval {...} called at ./645816.pl line 5
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Is something like:

use strict;
use warnings;

my $pos;

$SIG{ALRM} = 'doReport';
alarm (2);

eval {doFail ()};


sub doFail {
    while (1) {
        $pos = 1;
        $pos = 2;
        $pos = 3;
        $pos = 4;
    }
}


sub doReport {
    my ($package, $filename, $line, $subroutine) = caller 0;
    
    print "$line, $subroutine (pos = $pos)\n";
    exit;
}
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Prints:

15, main::doReport (pos = 2)
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what you are looking for?

Not a direct answer to your question, but perhaps Devel::Trace (or simply running under the debugger) might show up the offending portion of code?

I don't know. The information is surely available somewhere (since the program needs to resume after the handler exits), but it might not be easy to obtain.

You could trace the code using a debugger. Tracing displays each executed line as it is executed.

Alternatively, you could do some manual tracing. Put a few print statements in strategic locations — don't forget to turn off buffering — and run the program. Now that you have a better idea where the problem is, put more print statements in that area and run the program again. Repeat this process until you locate the problem. This is the same idea behind binary searches.

$SIG{ARLM} = sub { 
  my ($package,$file,$line)=caller;
  print "ALRM at $file:$line\n";
};
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