my @bits = split //, unpack "b*", $vec;

##</code><code>##

use integer;
my $vec = 42;
my @ints;
my $bits = unpack "b*", $vec;
my @bits = split //, unpack "b*", $vec;
push @ints, 0 if $bits =~ s/^(\d)// && $1;
push @ints, pos $bits while($bits =~ /1/g);

print "\n";
print join ', ', @ints;
print " <-- bit positions set\n";
print join ', ', @bits;
print " <-- bits \n";