my $rx = qr/
	(["'])		# save " or ' in $1
	(?:		   # group
		[\\]{2}	  # double escape
		|			# OR
		[\\]$1	   # escaped end of data
		|			# OR
		[\\][a-z]	# escaped letter ( escape sequence )
		|			# OR
		[^\\\n\r$1]  # other useable characters
	) *		   # end group, any times
	$1			# content of $1
/x;

# ...später dann...

$string =~ /^($rx)/;