Question

My usual ‘x’ usage was :

print("#" x 78, "\n");

Which concatenates 78 times the string “#”. But recently I came across this code:

while (<>) { print if m{^a}x }

Which prints every line of input starting with an ‘a’. I understand the regexp matching part (m{^a}), but I really don’t see what that ‘x’ is doing here.

Any explanation would be appreciated.

Answer 1

It’s a modifier for the regex. The x modifier tells perl to ignore whitespace and comments inside the regex.

In your example code it does not make a difference because there are no whitespace or comments in the regex.