#!/usr/bin/perl -n00
use strict;
use warnings;
our $snippet;
BEGIN {
    my $snippetfile = shift; # first file on command line
    open my $fh, '<', $snippetfile 
        or die "Can't read '$snippetfile': $!\n";
    $snippet = <$fh>; # get entire block into $snippet
    close $fh or die "Can't close filehandle of '$snippetfile' properly: $!\n";
}

if (/architecture/s) {
    print; # print current block
    print $snippet; # print snippet from file 1
} elsif (/signal/s) {
    print $snippet; # print snippet first
    print; # then the current block
} else {
    print;
}