User input as number or string in perl? - string

Question

I am new to perl. When I enter a number from command prompt, the variable in my script takes it as a number.
How do i make perl take the user input number as string?
I just want to check if the user entered string "1" and not number 1?
I wrote the code as follows:
#!usr/bin/perl
use strict;
use warnings;
print 'enter';
$a=<>;
if($a==1)
{
print 'Number entered';
}
elsif($a eq "1")
{
print 'Text entered';
}

Answer 1

Input from a file or from the console is always a string. You could check to see whether that string contains anything other than numeric characters, but you have to think about what you mean by entering a number.
Perl scalar variables behave as strings and numbers interchangeably and simultaneously. But with strings you have to get the comparison exactly right. An extra space at the beginning or end of the string will stop it from matching as you expect.
This program demonstrates
use strict;
use warnings;
my $aa = '1';
my $bb = 2;
my $cc = '3 ';
print $aa == 1 ? 'match' : 'no match', "\n";
print $aa eq '1' ? 'match' : 'no match', "\n";
print $bb == 2 ? 'match' : 'no match', "\n";
print $bb eq '2' ? 'match' : 'no match', "\n";
print $cc == 3 ? 'match' : 'no match', "\n";
print $cc eq '3' ? 'match' : 'no match', "\n";
output
match
match
match
match
match
no match
So Perl is quite happy saying that '3 ' is numerically equal to 3, but is is different from the string '3' because of the trailing space.
That is what is happening in your case. The value you enter into $a is something like "42\n", which Perl will happily convert to the number 42 for you. But if you compare it to the string '42' then it is different because it has a trailing newline.
You will want to use chomp almost invariably when you read input from a file, and especially from a console.
You should also indent your code properly to make it more readable.
Update
Data::Dumper is a very useful tool to see exactly what is in a string and why a string comparison isn't working. (Data::Dump is even better, but it isn't a core module and you may have to install it.)
If I run this program
use strict;
use warnings;
use Data::Dumper;
$Data::Dumper::Useqq = 1;
my $input = <>;
print Dumper $input;
chomp $input;
print Dumper $input;
and type abcEnter. Then the output is
$VAR1 = "abc\n";
$VAR1 = "abc";
which makes the trailing newline obvious.
Note that setting $Data::Dumper::Useqq to a true value is essential. Otherwise the output is little better than a simple print.