formline with a format would probably do it.

use strict;

my $str="Reports that say that something hasn't ".
        "happened are always interesting to me " .
        "because as we know, there are known knowns; ".
        "there are things we know we know. We also ".
        "know there are known unknowns; that is to ".
        "say we know there are some things we do not ".
        "know. But there are also unknown unknowns --".
        " the ones we don't know we don't know.";
        
my $picture = '^<<<<<<<<<<<<<<<<<<<< ~~'."\n";

formline ($picture, $str);
print "$^A\n";
[download]

Adjust the picture variable to suite your needs. If the number of chars is variable, it is fairly simple to construct the format using the 'x' operator

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