my %h => (
 X => { num => 1, txt => 'X' },
 Y => { num => 2, txt => 'Y' },
 Z => { num => 3, txt => 'Z' },
);

my $thr = threads->new(\&thr_func, \%h);

...LOOP-MAIN
#using the hash on in readonly mode (eg print all values from hash)
...END LOOP-MAIN

sub thr_func {
 my ($h_ref) = @_;
 ...LOOP-THR
 #using the hash on in readonly mode (eg print all values from hash)
 ...END LOOP-THR
}