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

my $find = '1.2.3';

open ( FH , "input" ) or die "$!";

while ( <FH> ) {
   chomp;
   my $input_line = $_;
   if ( grep ( /$find/i , $input_line ) ) {
     print "OUT :$input_line:\n";
   }
}



Input :-
Hello this is first sample 1.2.3
Hello this is second sample 1_2_3
Hello this is second sample 1.2.3.
Hello this is fourth sample_1_2_3_

Output :-
OUT :Hello this is first sample 1.2.3:
OUT :Hello this is second sample 1_2_3:
OUT :Hello this is second sample 1.2.3.:
OUT :Hello this is fourth sample_1_2_3_: