perl : making a script as efficient as a perl one-liner - perl

Question

I'm able to do this on the command line and it works :
~/Tools/perl/edif_extr_cell.pl design.edif nmos1p8v | perl -p -e 's/^/\n/ if /portImplementation|figure\s+device/;' | perl -n -000 -e 'print if /portImplementation/;'
(basically, extracting a section of the EDIF file).
Now, I want to make a utility of this. And my script is below. Question : can this code be more efficient? If feel like it's very inelegant. I could pipe streams easily on the command line but, in a script, I feel lost.
#!/usr/bin/perl -w -p
BEGIN{ $file = '';}
s/^/\n/ if /portImplementation|figure\s+device/;
$file .= $_;
END{
$cmd = q{\rm -f /tmp/dump}.$$.'.txt';
system( $cmd );
open( OUT, ">/tmp/dump$$.txt");
print OUT $file;
close OUT;
$out = `perl -n -000 -e 'print if /portImplementation/;' /tmp/dump$$.txt`;
system( $cmd );
print $out;
}

Answer 1

If I understand correct, you want to be able to do
~/Tools/perl/edif_extr_cell.pl design.edif nmos1p8v | myfilter
Ideally, you'd merge the two Perl scripts into one rather than having one script launch two instances of Perl, but this turns out to be rather hard because of the change to $/ (via -00) and because you insert newlines in the first filter.
The simplest answer:
#!/bin/sh
perl -pe's/^/\n/ if /portImplementation|figure\s+device/' |
perl -00ne'print if /portImplementation/'
It appears that you were trying to write the equivalent of that sh script in Perl. It would look like the following:
#!/usr/bin/perl
use strict;
use warnings;
use IPC::Open qw( open3 );
# open3 has issues with lexical file handles.
pipe(local *PIPE_READER, local *PIPE_WRITER)
or die($!);
my $pid1 = open3('<&STDIN', '>&PIPE_WRITER', '>&STDERR',
'perl', '-pes/^/\n/ if /portImplementation|figure\s+device/');
my $pid2 = open3('<&PIPE_READER', '>&STDOUT', '>&STDERR',
'perl', '-00neprint if /portImplementation/');
waitpid($pid1);
waitpid($pid2);
I'd normally recommend IPC::Run3 or IPC::Run for launching and interfacing with child processes, but low-level open3 does the trick nicely in this particular situation.

Answer 2

I downloaded a random EDIF file from GitHub, running the following script on it gives the same output as your code:
#! /usr/bin/perl
use warnings;
use strict;
my #buffer;
my $found;
my $prepend = q();
while (<>) {
if (/portImplementation|figure\s+device/) {
if ($found && #buffer) {
print $prepend, #buffer;
$prepend = "\n";
}
undef $found;
#buffer = ();
}
$found ||= /portImplementation/;
push #buffer, $_;
}
# Don't forget to output the last paragraph!
print $prepend, #buffer if $found && #buffer;