_____________________________________________________
Jeff[japhy]Pinyan: Perl, regex, and perl hacker.
s++=END;++y(;-P)}y js++=;shajsj<++y(p-q)}?print:??;

my( $start )= /^(.{0,199}\S)\s/;

my $tmp = substr($_,0,200);
$tmp =~ s/\s+\w*$//g;
[download]

$ perl -e 'do() || ! do() ;'
Undefined subroutine &main::try
[download]

This appeals to the thug in me :) Q: is there a processor saving in using substr rather than a regex?

§ George Sherston

A massive amount, substr has a hell of a lot simpler job to do.

    Benchmark: timing 500000 iterations of regexp, substr...
        regexp: 11 wallclock secs (10.16 usr +  0.00 sys = 10.16 CPU) 
+@ 49236.83/s (n=500000)
        substr:  1 wallclock secs ( 0.90 usr +  0.00 sys =  0.90 CPU) 
+@ 554938.96/s (n=500000)
[download]

gav^

Q: is there a processor saving in using substr rather than a regex?

In general yes, but not if you have to combine the substr with a regex (as MZSanford does here).

The benchmark shows that the pure regex approach suggested by tye is quickest for your problem, closely followed by japhy's version using fancier regex constructs. MZSanford's substr/substitute is slow (and a bit buggy, fixed that below :) because it tries to start the match at every interior whitespace. But you can improve on it: ($chunk) = substr($string,0,201) =~ /(.*)\s+\w*$/',

Here are the results of the benchmark:

Benchmark: running Hofmator, MZSanford, japhy, tye, each for at least 
+3 CPU seconds...
  Hofmator:  3 wallclock secs ( 2.99 usr +  0.01 sys =  3.00 CPU) @ 20
+6100.67/s (n=618302)
 MZSanford:  4 wallclock secs ( 3.03 usr +  0.00 sys =  3.03 CPU) @ 55
+936.63/s (n=169488)
     japhy:  4 wallclock secs ( 3.00 usr +  0.00 sys =  3.00 CPU) @ 25
+6036.67/s (n=768110)
       tye:  4 wallclock secs ( 3.00 usr +  0.00 sys =  3.00 CPU) @ 29
+2146.67/s (n=876440)
[download]

generated by this code:

#!/usr/bin/perl
use Benchmark qw/timethese/;
 
$string = q/Some text repeated / x 50;

timethese(-3, {
    MZSanford => '$chunk = substr($string,0,201);$chunk =~ s/\s+\w*$//
+',
    Hofmator  => '($chunk) = substr($string,0,201) =~ /(.*)\s+\w*$/',
    japhy     => '($chunk) = $string =~ /^(.{1,200})(?<!\s)(?!\w)/;',
    tye       => '($chunk) = $string =~ /^(.{0,199}\S)\s/',
});
[download]

-- Hofmator

How can I split a line on word boundaries closest to a certain length?

($text) = $var =~ /^(.{200})(?:\s+\w*)?/s;
print $text.$/;
[download]

broquaint

Update: apparently you can ;o)

use strict;
use warnings;

my $text = q{
I need to extract the first several words from a paragraph of text con
+tained in a $var, 
so as to get the longest extract that's less than or equal to 200 char
+acters. 
My brute-force-and-ignorance method is: blah some more text here etc e
+tc
};

my $chunk;

($chunk) = $text =~ /^(.{1,200})(?<!\s)(?!\w)/;

printf "[%d] %s\n", length($chunk), $chunk;

$chunk = $text;

$chunk =~ s/^(.{200}).*$/$1/;
$chunk =~ s/^(.*)\s+\w*$/$1/;

printf "[%d] %s\n", length($chunk), $chunk;

$chunk = "";
$text =~ s/^\s+//;

foreach (split /\s+/, $text) {
    if (length($chunk) + length($_) <= 200) {
        $chunk .= $_ . " ";    
    } else {
        last;
    }
}

chop $chunk;
printf "[%d] %s\n", length($chunk), $chunk;
[download]

Use of uninitialized value in length at C:\temp\ws.pl line 15.
Use of uninitialized value in printf at C:\temp\ws.pl line 15.
[0] ''
[242] '
I need to extract the first several words from a paragraph of text con
+tained in
a $var,
so as to get the longest extract that's less than or equal to 200 char
+acters.
My brute-force-and-ignorance method is: blah some more text here etc e
+tc
'
[194] 'I need to extract the first several words from a paragraph of t
+ext contai
ned in a $var, so as to get the longest extract that's less than or eq
+ual to 200
 characters. My brute-force-and-ignorance'
[download]

gav^