my $len = 20;
# 345678901234567890
my $text = <<'ENDTXT';
One
Two Three Four Five Six Seven
Eight Nine Ten
Eleven Twelve Thirteen Fourteen
ENDTXT

my @lines = $text =~ /(.{1,$len}\W)/gm;

# remove leftover whitespace at ends of lines
s/\s+$// for @lines;

print "<$_>\n" for @lines;
__END__
<One>
<Two Three Four Five>
<Six Seven>
<Eight Nine Ten>
<Eleven Twelve>
<Thirteen Fourteen>