Rerun perl -c with warnings unused

perlc.pl

#!/usr/bin/env perl

use Modern::Perl;
use File::Temp 'tempfile';
use IO::All;

my $libcustom = '.libcustom';

# run the code with perl -c and show STDERR if it fails. Otherwise, rerun it
# with perl -c -Mwarnings::unused

my $prog = shift // die "Usage: $0 perlfile";

my $PERL5LIB = $ENV{PERL5LIB} // '';
if ( -f $libcustom ) {
    chomp( my @libs = io($libcustom)->slurp );
    $PERL5LIB = join ':' => $PERL5LIB, @libs;
}

my ( undef, $tempfile ) = tempfile();

my $perl    = "PERL5LIB=$PERL5LIB perl ";
my $command = "$perl -c $prog 2>$tempfile 1>$tempfile";

# if anything goes to STDERR by the program completes successfully, don't show
# anything because we're going to rerun with warnings::unused and we don't
# need to duplicate the messages to STDERR                                                                                      
my $error = system($command);
$error and do {
    print io($tempfile)->slurp;
    exit $error;
};
$command = "$perl -Mwarnings::unused -MVi::QuickFix -c $prog";
system($command);