Search for keyword and then conditional on finding it search for another keyword from a list of words using Perl [closed] - perl

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My question concerning Perl is very similar to the one involving Python answered here:
How can I search within a document for a keyword and then subsequent key words within a set number of lines of the original keyword in Python?
This involves searching for one keyword and then for another from a list of keywords (say you have a list of 4 words) in the vicinity of the original keyword (say plus minus 5 lines) and then when matched printing out a range of lines (say plus minus 20 lines from the original keyword)
Two extensions if possible:
Ext 1: in the printout highlight key words
Ext 2: search all files from a directory and add the filename to the printout (filename in one line, followed by the lines extracted from the file)
I would appreciate even if directed to similar examples...

Answer 1

Read in the File as a nice array:
my #line = <FILE>;
Search for the 1st word:
my $i;
foreach $i (0 .. $#line) {
last if $line[$i] =~ /$firstWord/i;
}
Get the surrounding using an array slice:
my #surrounding = #line[$i-5 .. $i+5];
One should however use some index checking like
[0<=$i-5 ? 0 : $i-5 .. $i+5<#line ? $i+5 : $#line]
repeat
Profit
The rest is left as an exercise to the reader.
For highlighting write
$line[$i] =~ s{($firstWord)}{<strong>$1</strong>};
or similar, depending on your output medium. map is your friend for this.