Question

I have a quick question. What am I doing wrong in below code:

#!/usr/bin/perl -w
use strict;
my $num = "12345";
print "$num \n" if $num =~ m/\d{1,3}/;

As my number is 5 digits long, I was hoping that the output should not print anything because if statement is looking for a number with at least 1 digit and maximum 3 digits. But my script pints the output as below:

# perl num.pl 
12345 

Am I misunderstanding the above regex?

Thanks.

EDIT:

So ,Actually I am trying to match an IP address like string. e.g. i want to match 11.222.3.444 but it did not work with m/\d{1,3}.\d{1,3}.\d{1,3}.\d{1,3}/
so i started working on a single string containing only the number and hence then posted this on the stack overflow.

If i have to put ^ OR $ then how should i go about using them if I want to match IP address like string s mentioned above.

Thanks for you time.

Answer 1

What your perl code says is, “inside the string $num can you find a string at least 1 character at most 3 characters made only of numbers.” The answer of course is yes.

What you want is

print "$num \n" if $num =~ m/^\d{1,3}$/;

Which means “inside the string $num starting at the first character and going to the last character is there a string at least 1 character long at most 3 characters long made only of numbers.”

If you are trying to find something like an ip address
regexp to match IP address is a good discussion of how to do that.