Very interesting indeed. It looks like B::Deparse doesn't fully understand the magic associated with the /x regex modifier. With /x, a literal \n and the two character sequence '\n' are not actually equivalent. B::Deparse isn't making that distinction.

Below, the second regex is the result of running the first one through B::Deparse. As this example shows, they are not the same.

#!/usr/bin/perl -wT
use strict;

my $v1 = my $v2 = "abcdef";

$v1 =~ s/c
d//x;               # original pattern: literal \n is gobbled by /x
                    # equivalent to the non-x: s/cd//;

$v2 =~ s/c\nd//x;   # deparsed version: interpolated "\n" is not touch
+ed by /x
                    # equivalent to the non-x: s/c\nd//;

print "V1 = '$v1'\n";
print "V2 = '$v2'\n";

=OUTPUT
V1 = 'abef'
V2 = 'abcdef'
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-Blake