Extract first 50 words from a string (Perl) [closed] - perl

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I write in Perl.
I need to split a string into first 50 words (or the entire text if there is less than 50 words total) and the rest words (empty string if the first is not above 50 words).
In the first part (first 50 words) and the second part (the rest) the word separators should be preserved: newline should remain newline and space should remain space.

Answer 1

Assuming that by word you mean just a sequence of non-whitespace characters, this can be done simply using a single regex. The one below looks for N-1 consecutive sequences of non-whitespace characters followed by whitespace characters, and then a further stretch of non-whitespace characters. This is the first part of the string. Any following whitespace is skipped, and then the rest of the string forms the second part.
I have used the /s modifier so that a dot . within the regex matches any characters, including newlines. The /x modifier allows for insignificant whitespace within the regex to make it more readable.
Thanks to #knarf for the data.
use strict;
use warnings;
my $text = 'Lorem ipsum dolor sit amet, consectetuer adipiscing
elit. Donec hendrerit tempor tellus. Donec pretium posuere
tellus. Proin quam nisl, tincidunt et, mattis eget, convallis nec,
purus. Cum sociis natoque penatibus et magnis dis parturient montes,
nascetur ridiculus mus. Nulla posuere. Donec vitae dolor. Nullam
tristique diam non turpis. Cras placerat accumsan nulla. Nullam
rutrum. Nam vestibulum accumsan nisl.';
my ($first, $rest) = wsplit($text, 50);
print $first, "\n\n";
print $rest, "\n";
sub wsplit {
my ($s, $n) = #_;
--$n;
$s =~ / ( (?: \S+ \s+ ){0,$n} \S+ ) \s* (.*) /xs;
}
output
Lorem ipsum dolor sit amet, consectetuer adipiscing
elit. Donec hendrerit tempor tellus. Donec pretium posuere
tellus. Proin quam nisl, tincidunt et, mattis eget, convallis nec,
purus. Cum sociis natoque penatibus et magnis dis parturient montes,
nascetur ridiculus mus. Nulla posuere. Donec vitae dolor. Nullam
tristique diam non turpis. Cras placerat
accumsan nulla. Nullam
rutrum. Nam vestibulum accumsan nisl.

Answer 2

I came up with this naive way but I guess there's a better one using a single regex.
use strict;
use warnings;
use Data::Dumper;
my $text = 'Lorem ipsum dolor sit amet, consectetuer adipiscing
elit. Donec hendrerit tempor tellus. Donec pretium posuere
tellus. Proin quam nisl, tincidunt et, mattis eget, convallis nec,
purus. Cum sociis natoque penatibus et magnis dis parturient montes,
nascetur ridiculus mus. Nulla posuere. Donec vitae dolor. Nullam
tristique diam non turpis. Cras placerat accumsan nulla. Nullam
rutrum. Nam vestibulum accumsan nisl.';
sub wsplit {
my ($s, $words) = #_;
my $pos = length $s;
my $n = 0;
while ($s =~ /\S+/g) {
$n++;
if ($n == $words) {
$pos = pos $s;
last;
}
}
return [substr($s, 0, $pos), substr($s, $pos)]
}
print Dumper(wsplit($text, 8));
Output:
$VAR1 = [
'Lorem ipsum dolor sit amet, consectetuer adipiscing
elit.',
' Donec hendrerit tempor tellus. Donec pretium posuere
tellus. Proin quam nisl, tincidunt et, mattis eget, convallis nec,
purus. Cum sociis natoque penatibus et magnis dis parturient montes,
nascetur ridiculus mus. Nulla posuere. Donec vitae dolor. Nullam
tristique diam non turpis. Cras placerat accumsan nulla. Nullam
rutrum. Nam vestibulum accumsan nisl.'
];