I think the following program takes care of the edge case too: when you have the first and second word in the right order and then the first word comes again and is not followed anymore by the second word. The OP made clear that he only had to look for the last occurrence of the first word.
use Modern::Perl '2014';

my $first  = qr/STRING/;
my $second = qr/MAGIC/;
my $first_pos;
my $second_pos;

while (<DATA>) {
    $first_pos  = $. if /$first/;
    $second_pos = $. if /$second/;
}

if ( $first_pos and $second_pos > $first_pos ) {
    say "Success! STRING at $first_pos followed by MAGIC at $second_po
+s";
}
else {
    say "Failure! (STRING: $first_pos - MAGIC: $second_pos)";
}

__DATA__
First line
second line
here is the STRING
empty text
the STRING again!
followed by the  MAGIC word
more emptiness
Oh no! the first STRING again
sadness
did we look in vain?
Ah, MAGIC success

[download]
To test the edge case, delete the last line of the DATA-section.

I have assumed that the first and second words cannot happen in the same line.

CountZero

A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James

My blog: Imperial Deltronics

In reply to Re: Detect Two Strings in File by CountZero
in thread Detect Two Strings in File by omegaweaponZ

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