$ perl -e'
    my $host = "localhost";
    eval $ARGV[0];
' 'system("echo", $host)'
localhost

##</code><code>##

$ perl -MTemplate -e'
    Template->new()->process(
        \$ARGV[0],
        { host => "localhost" },
        \my $cmd
    );
    system($cmd)
' 'echo [% host %]'
localhost