#!/usr/bin/perl

my %hash1 = ( key1 => val1,
              key2 => val2,
              key3 => val3,
              key4 => val4,
              key5 => val5);
              
my %hash2 = ( key1 => xxxval1,
              key2 => xxxval2);
            
out:foreach my $key (keys %hash1)
{
        foreach my $inkey (keys %hash2)
        {
                if($key eq $inkey)
                {
                        $hash1{$key} = $hash2{$inkey};
                        next out;
                }
        }
}