input is:
A0000.f BG_c22
A000X.f BG_c5
A000X.r BG_c5
A002B.f BG_c38
A002B.r BG_c38
A003A.r BG_c38
A0082.r BG_c12
A00AS.f BG_c52
A00B9.f BG_c45
A00B9.r BG_c45
A00DK.f BG_c5
A00F0.f BG_c22
A00F0.r BG_c22
A00F3.f BG_c14
A00FX.f BG_c7
A00FX.r BG_c7

result shud be:
A0000.f BG_c22
A003A.r BG_c38
A0082.r BG_c12
A00AS.f BG_c52
A00DK.f BG_c5
A00F3.f BG_c14

##</code><code>##

#!/usr/bin/perl
use strict;
use warnings;
open(FILE,"pe_real_sample.txt") or die "cannot open";
open(OUTFILE,">last.output") or die "cannot open";
my @arr=<FILE>;
close(FILE);
my $prev1=0;my $prev2=0;my @dels;
foreach(@arr){
	my @spl=split(".(f|r)",$_);
	if($prev1 eq $spl[0] && $prev2 eq $spl[2]){
		push(@dels,$spl[0]);
	}
	$prev1=$spl[0];$prev2=$spl[2];
}
my $del= join '|', map quotemeta, @dels;
my @arr1=grep !/$del/,@arr;
print OUTFILE "@arr1\n";