Perl How to: Find a Given Variable String is numeric or not

This tutorial explains How to check given string is a number or not in Perl with Code examples

• Scalar::Util module provides the qw(looks_like_number)function that checks given variable is a number or not. For example, looks_like_number("111") returns a boolean value, use in the conditional if statement to check as a number or not.
• Second, append a variable with zero, and use the result in a conditional if statement.
• Third, use the [Regexp::Common] module that uses a regular expression for real and integer numbers.

You can check my previous post, on How to Convert String to Number in Perl.

Dart How to check whether a String is Numeric or not

This approach uses the parse method of double for floating and number for without decimals

The Scalar::Util module has a function looks_like_number internally uses converts string literal into a number and checks result is a number or not. looks_like_number

Here is an example isNumeric Extension method on the String class

use warnings;
use strict;

use Scalar::Util qw(looks_like_number);

my $var1="123";
print "$var1 contains", looks_like_number($var1) ? '' : ' not', " a number\n";
print "a",looks_like_number($var1),"test";

my $var2="abc";
print "$var2 contains", looks_like_number($var2) ? '' : ' not', " a number\n";

my $var3="1a23";
print "$var3 contains", looks_like_number($var3) ? '' : ' not', " a number\n";

my $var4="__";
print "$var4 contains", looks_like_number($var4) ? '' : ' not', " a number\n";

Output:

123 contains a number
a1testabc contains not a number
1a23 contains not a number
__ contains not a number

Second Approach; using regular expression

Regexp::Common module functions to process and test regular expressions with values in Perl. First, Install this module into your environment using the below code.

 cpan Regexp::Common

Next, use this in your code. It checks for real and floating numbers using regular expressions. $RE{num}{real} is a pattern that checks for real numbers. Also, use $RE{num}{int}, for Checking integer.

Here is an example

 use warnings;
use strict;
use Regexp::Common;

is_number("111");
is_number("abc");
is_number("123.11");

# Sub routine for Checking a Number 
sub is_number {
    if ($_[0] =~ /$RE{num}{real}/) {
        print "$_[0] is a number\n";
    }
    else{
        print "$_[0] is not a number\n";
     }
}

The third approach, append a variable with zero using the + operator, Check result is equal to a numeric value. You have to compare with a given value, So It is not recommended to use this approach Here is an example.

use warnings;
use strict;

use Scalar::Util qw(looks_like_number);
my $var1="123";
if ( $var1 + 0 eq 123) {
    print "$var1 is a number\n";
}
else{
    print "$var1 is not a number\n";
}