From "The most precise second (timer)", which choroba linked to, see my post here which demonstrates clock_nanosleep from Time::HiRes.

You don't mention what's supposed to happen when your function happens to take longer to execute than 0.1 seconds?

use warnings;
use strict;
use Time::HiRes qw/ clock_gettime clock_nanosleep
    CLOCK_REALTIME TIMER_ABSTIME /;
die "Don't have nanosleep" unless Time::HiRes::d_nanosleep();

use Time::HiRes qw/usleep/; # just for this fake "myfunc"
sub myfunc {
    printf "fired %.2f\n", clock_gettime(CLOCK_REALTIME);
    my $delay_us = int(rand 100000)+10000; # 110000us = 0.11s
    printf "delay %.2fs\n", $delay_us/1e6;
    usleep $delay_us;
}

my $next_s = int(clock_gettime(CLOCK_REALTIME))+1;
my $interval_s = 0.1;

my $run = 1; $SIG{INT} = sub { $run = 0 };
while ($run) {
    my $now_s = clock_gettime(CLOCK_REALTIME);
    $next_s += $interval_s while $next_s < $now_s;
    clock_nanosleep(CLOCK_REALTIME, $next_s*1e9, TIMER_ABSTIME);
    myfunc();
}
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Update: Note that since the above code uses floating-point numbers there's a small chance for errors there. If that's a concern, you can switch to nanoseconds, since that's what clock_nanosleep takes anway.