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

my @arr = ( {'a' => 'x', 'b' => 'y', 'c' => 'z'}, 
            {'a' => 'x1', 'b' => 'y1', 'c' => 'z1'} ) ;
my %h = map {;"$_->{'a'}_$_->{'c'}" => $_->{'b'} } @arr ;
print "$_ -- $h{$_}" foreach ( keys %h ) ;