P:\test>perl5.6.1 -Mstrict -wle 
"my $s= '<object>' x 160_000; print 'Ok' if $s =~ m[^(?:<object>)+$]"
Ok

P:\test>perl5.8.4 -Mstrict -wle 
"my $s= '<object>' x 160_000; print 'Ok' if $s =~ m[^(?:<object>)+$]"
Ok

P:\test>perl5.8.4 -Mstrict -wle 
"my $s= '<object>' x 160_000; print 'Ok' if $s =~ m[^(?:<object>){160000}$]"

Quantifier in {,} bigger than 32766 in regex; 
marked by <-- HERE in m/^(?:<object>){ <-- HERE 160000}$/ at -e line 1.