I can confirm the leak here too (Linux), with something as simple as the following, on Perl versions 5.18 and up, earlier versions don't leak. Definitely report this via perlbug.

#!/usr/bin/env perl
use warnings;
use strict;

for ( 0..500 ) {
    for ( 0..1000 ) {
        (my $x = "x") =~ s/\x{2122}/(TM)/sg;
    }
    system("ps -hovsz $$");
}
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