Another way to do it:

my $var = 'x' x 1_000;
my $var_length = length $var;
my $max_length = 100;

for ( my $offset = $var_length - $var_length % $max_length; $offset >=
+ 0; $offset -= $max_length ) {
    substr $var, $offset, 0, "\n";
    }

print "$var\n";
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