1. Perl
  2. Numerical value
  3. here

Determine if the string represents an integer

To determine if string represents an integer, regular expression > Is used. Determines if a regular expression is made up of numbers from start to finish.


To determine if it's an integer, just add to the regular expression above that it doesn't matter if it's prefixed with + or-.

/^[+-]? [0-9]+$/


This is an example to judge whether a variable is a numerical value.

use strict;
use warnings;

print "1: Determine if the string represents the correct number\n";

my $num1 = "345";
# Determining if the string is only numbers
# Read "One or more numbers continue from the beginning to the end"
if ($num1 =~ /^[0-9]+$/) {
  print "$num1 is a string of numbers only.\n";

# Judgment whether it is an integer
my $num2 = "-123";

# "With or without + or-at the beginning, after that
# One or more numbers follow to the end "
if ($num2 =~ /^[+-]? [0-9]+$/) {
  print "$num2 is an integer.\n";

Related Informatrion