use strict;
use warnings;

my $t1;
my $t2;

$t1 = $t2 = q{3} x 33335 . q{7};
print qq{Sequences of 3s:-\n};
print qq{>@{ [ length $1 ] }<\n}
   while $t1 =~ m{(3+)}g;
print q{-} x 50, qq{\n};

1 while $t1 =~ s{\G((?:3{4})+)}{ qq{[@{ [ length $1 ] }]} }eg;
print qq{With 1 while and \\G\n$t1\n@{ [ q{-} x 50 ] }\n};

$t2 =~ s{((?:3{4})+)}{ qq{[@{ [ length $1 ] }]} }eg;
print qq{Without either\n$t2\n@{ [ q{=} x 50 ] }\n};