To demonstrate how to break on more than one delimiter (in this case blanks and curly braces), here is a twist on gryphon's code...

sub split_delimited {
    my $input = shift;
    my $limit = shift;
    my @output;
    my $s = '';
    my $t = '';
    my $bracket_count = 0;
    my $build_var;

    $input =~ s/\n/ /gm;
    foreach ( split ( //, $input ) ) {
        $build_var .= $_;
        if (/\{/) {
            $bracket_count++;
        }
        elsif (/}/) {
            $bracket_count--;
        }
        elsif ( / / and $bracket_count == 0 ) {
            push @output, $build_var if ( $build_var and $build_var ne
+ ' ' );
            $build_var = '';
        }
    }
    foreach  (@output) {
        if (length($s) < $limit) {
            $s .= $_;
        }
        else {
            $t .= $_;
        }
    }
    return $s,$t;
}
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This returns two substrings without violating any of the formatting within the parent string, but still solving whatever problems being over the 'limit' would cause.

As was pointed out, there are a number of module approaches to this problem, but given the constraint you mentioned, I wouldn't hesitate to use this code— In fact I did, thanks gryphon!

hsm

BTW, your example is delimited, but I think I know what you meant…