use strict;
use Data::Dumper;


%muthash = (
        key1 => '1',
        key15 => '3',
        key150 => '1', );
%copyhash =(
        key1 => '1',
        key15 => '1',
        key140 => '1', );
%mergedhash = ();
%mergedhash = map {$_=> $muthash{$_} + $copyhash{$_}; } (keys %muthash, keys %copyhash);
print Dumper(\%mergedhash);