Since my chow break broke our conversation, for starters: I erred on the CB; I don't much care for the code you snagged from Q&A, except the regex, which may be useful to you if you have long lines.

That said, the code below, modified from the same Q&A node (code example #4) will be a starting point for you. Please come back and edit your OP with a small sample of data (inside code tags).

Since you didn't supply that, I've dummied up a small text and have used it in the __DATA__ section below. That section is a stand-in for your datafile; you won't do it that way, given the size of your data files but as an example, it'll serve (I hope) If your post-division data files are something like 69MB (as I think you mentioned), you'll need a lot of RAM or you'll need to read in groups of lines (segments) or even single lines. Alternately Re: Array size too big? may spark some ideas abut the file splitting you've already done.

Also tell us why the search term itself is inadequate; i.e., why you want some words around it.

#!/usr/bin/perl
use strict;               # using strict and warnings will help you sp
+ot typos and other guff
use warnings;
use 5.024;

# 1204380

my $string = 'tryna';       # you didn't give us an example of the dat
+a so using this
my (@slurp, $line, @found); # declare vars; bad for to do as globals, 
+but simpler to read
@slurp = <DATA>;                    # read each line of __DATA__ into 
+var $slurp;
for $line(@slurp) {                 # read thru array @slurp line by l
+ine
    if( $line =~ m/($string)/gs ) { # if the current line contains $ s
+tring
        push @found, $line;         # and push it to array, @found 
    }
 }
say @found;              #  ... whose elements get printed to console,
+ here.
                         # you can redirect the scripts output to a fi
+le or write a
                         # few more lines here to have the script writ
+e it to a file
                         # or, of course, you can use any one of many 
+methods to 
                         # catch JUST the searchstring and surrounding
+ words (why?")

# NB: this will cause a warning about an unitiialized var in Line 5; 
# simple enuf but not immediately an issue for OP and, IMO, adding ano
+ther loop 
# will just be confusing at this time.

__DATA__

123456 7890 abcd3e fc this sentence has for bar tryna much too long fo
+r my taste
this doesn't have the magic phrase 123456 7890 abcd3e fc.
much too long for my taste but tryno tryna foo bar baz bat bingo and h
+as the magic phrase
endit
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