use feature ":5.14";
use warnings FATAL => qw(all);
use strict;
use Data::Dump qw(dump pp);

my %a = qw(key1 val1 key2 val2 key3 val3);
my %b = qw(val1 val5 val2 val6 val3 val7 val4 val8);

my %c = %{{map {($_, $b{$a{$_}})} keys %a}};

pp(\%c)

##</code><code>##

{ key1 => "val5", key2 => "val6", key3 => "val7" }