If detach doesn't work with older perls does that mean I have to resort to using a shared variable to tell the thread to exit? I'd really like to avoid doing that if possible.

You apparently have no problem with killing the threads ungracefully (->detach()). If you have no problems killing the main thread ungracefully either, just use POSIX::_exit instead of exit.

#!/usr/bin/perl

use threads;
use POSIX qw( _exit );

sub worker { sleep() while 1; }

$SIG{INT} = sub { _exit(0) };
my $thread = threads->create('worker')->detach();
print("Press Ctrl-C to exit\n");
sleep() while 1;
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