#! /usr/bin/perl 

use strict ;
use warnings ;

my @inp = ("abc_A_bla", "abc_B_bla", "abc_C_bla") ;

my %inp ;

$inp{$_} = 1 grep ( /\w{3}_(\w)/, @inp ) ;

foreach ( keys %inp ) {
	print "Found $_\n" ;
}