Changing the behaviour of your regex: Modifiers

Modifier	Meaning
/i	Ignore case in match
/s	Let `.` match newline and ignore depricated `$*` variable
/m	Let `^` and `$` match next to embedded `\n`
/x	Ignore whitespace and comments in regex
/o	Compile pattern once only.

The modifies go at the end of a regex operator. e.g. m/unix/i matches unix, UNIX, Unix, uNIx, etc.

The /x modifier helps for readability:

	m/^(\(\d{3}\))?\d{3}-\d{4}$/;

matches the same thing as:

	m/
	  ^		# The match must be at the very beginning
	  (		# Start of a group
	    \(		# Literal (
	    \d{3}	# Exactly three digits
	    \)		# Literal )
	  )?		# The group may or may not be present in the match
	  \d{3}		# Exactly three digits
	  -\d{4}	# followed by a hyphen and four more digits
	  $		# The match must be at the very end
			# in this case the match must be the whole string
	/x;		# Remove comments and compress all excess whitespace

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