cmpthese requires an anonymous hash, whose values are subs to execute. This should be better.

#!/usr/bin/perl -w
use strict;
use Benchmark qw(cmpthese);

my $file1 = 'first.pl';
my $file2 = 'second.pl';

cmpthese (-5,
{
    'first' => sub {
        chdir "/home/firstdir/";
        do  $file1},
    'second'=> sub {
        chdir "/home/seconddir/";
        do $file2}
});
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