Seconded what ww said.

You might be able to narrow down the point where the program is stuck by trapping the INT (interrupt) signal, then typing ^C when the CPU goes to 100%, and looking at the stack trace.  (See caller for more details).

For example:

use strict;
use warnings;

$SIG{INT} = sub {
    my (@stack, $level);
    while (1) {
        my ($pkg, $fn, $ln, $sub) = caller($level++);
        if (!($pkg or $fn or $ln or $sub)) {
            for (my $i = 0; $i < @stack; $i++) {
                print " " x $i, $stack[$i], "\n";
            }
            exit;
        }
        unshift @stack,  "-> $pkg: $fn (line $ln) sub $sub";
    }
};


# Your program here ....
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