use strict;
use warnings;

undef $/;
my $text = <DATA>;

my @result = map { m/'(.*?)'/g } grep /source/, split /\n/, $text;

use Data::Dumper;
print Dumper \@result;

__DATA__
'pfad'
source 'pfad2'
was soll passieren, wenn es 2 'pfade' 'gibt'? 
source 'pfad3' 'pfadX'
'pfad4' source
was ganz angeres
und 'nochwas' anderes