My Regex-1 matches the string although string has a space between "builtin.c \". I do understan why Regex-2 will match and Regex-2 will not. But I do not get why Regex-1 is matching. Please see my commented code for detaisl of the question. Thank you for your wisdom!

#!/usr/bin/perl
use warnings;
use strict;
use 5.010;

my $string = 'SRC=array.c builtin.c \
missing.c msg.c';

#Regex-1 Following matches, but WHY? String has a single space between
+ "builtin.c \"
$string =~ m/^\w+=[^\n\\]*\\/;

#Regex-2 Following also matches
$string =~ m/^\w+=[^\n\\]* \\/; #pay attention to single space between
+ * and \

#Regex-3 Following does NOT match
$string =~ m/^\w+=[^\n\\]*  \\/; #pay attention to double spaces betwe
+en * and \

say $string;
[download]