This "one pass" solution is obviously inspired by people like Grandfather, but this is a solution I can understand *^^*:

#!/usr/bin/perl
use warnings;
use strict;

use List::Util;

package main;


my $max = 21;
my @nums = (1, 5, 6, 8, 15, 20);
my $pad = 1; # lines of context on each side

my $last = -1 - $pad;

foreach ( @nums ) {
    my $start = List::Util::max 1, $_ - $pad, $last + 1;
    my $end = List::Util::min $max - 1 , $_ + $pad;
    next if ( $start > $end );
    for ( my $i = $start; $i <= $end; $i++ ) {
    if ( $i == $_ ) {
        print "Highlighted $i\n";
    }
    else {
            print "Line $i\n";
    }
    }
    $last = $end;
}

[download]
The output is:

C:\Code>perl mintest.pl
Highlighted 1
Line 2
Line 4
Highlighted 5
Line 6
Line 7
Highlighted 8
Line 9
Line 14
Highlighted 15
Line 16
Line 19
Highlighted 20

[download]

In reply to Re^3: Padding search results with context by dwm042
in thread Padding search results with context by moritz

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.