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

my $fileName = "file_detail.txt";
open my $fOut, '>', $fileName or die "Can't create '$fileName': $!\n";
print $fOut <<CONTENT;
123
abc
12ab3c
CONTENT
close $fOut;

open (my $fh, "<", $fileName);

while (defined (my $value = <$fh>)) {
    chomp ($value);
    if ($value eq "abc") {
        print "matched 'abc'\n";
    } elsif ($value eq "123") {
        print "matched '123'\n";
    }
}

##</code><code>##

matched '123'
matched 'abc'